The 2015 MotoGP season kicks off tomorrow. On Wednesday, the riders take to the track once again at Sepang to continue the development on the bikes they will be racing this year, and to test out the new updates the engineers have been working on during the winter break.

And yet the two most important and interesting developments won't even be at the first Sepang test. Ducati's much-anticipated Desmosedici GP15 is not quite ready for prime time, and so will not make its public debut until 19th February at the launch in Bologna, and not make its first laps in public until the second Sepang test at the end of this month. Yamaha's fully seamless gearbox – allowing both clutchless upshifts and downshifts – will also wait until Sepang 2 before Valentino Rossi and Jorge Lorenzo get their hands on the bike.

The official reasons given for the delay are that the GP15 and Yamaha's gearbox are almost ready, but not quite, still needing a few last checks by the engineers before they are ready to be handed over to the factory riders. Those of a cynical – or perhaps even paranoid – bent may be tempted to speculate that the delays are more to do with the media than the engineering. The first Sepang test this week is well-attended by journalists and photographers alike, the MotoGP press just as eager as the riders and the fans for the winter to be over.

The second Sepang test sees only a very few journalists attend, with few publications willing to spend the money to cover the expenses for what is often just more of the same. Perhaps the factories have cottoned on to this, and are taking advantage of the opportunity to test important new parts with a little less media attention. Or perhaps it really is just a case of not being quite ready in time.

Despite the absence of the really big news, there will still be plenty to see. So who will be testing what, and what are the key factors to keep an eye on?

Yamaha

Without the fully seamless gearbox, does Yamaha still have much to test? The answer is yes, but the changes will be subtle, and hard to spot without access to a large archive of photos of the 2014 bike to compare it to.

Yamaha did a lot of work during 2014 to make up for the ground they lost with the reduction of the fuel allowance to 20 liters and the introduction of the new Bridgestone tires with the heat-resistant layer. Those changes both damaged Yamaha's traditional strong point, its corner speed. By the end of the year, Yamaha had smoothed out the power delivery and regained some of the edge grip they lost with the Bridgestones, and were good enough to outscore the Hondas in the final races.

They also made major improvements in their weakest area, in braking. The Yamaha YZR-M1 likes to brake early, carry a lot of speed into the corner, then sweep round in a wide arc. The trouble which Jorge Lorenzo and Valentino Rossi faced was that all too often, when they released the brakes to start entering the corner, they would find a Honda in the way, the RC213V allowing its riders to brake when they saw God, to paraphrase Kevin Schwantz.

The 2014 M1 was already a lot better in this respect, the focus of the development for 2015 was to improve even further. The fully seamless gearbox is a major part of that equation, but changes to swingarm and chassis will also play a role.

For Jorge Lorenzo and Valentino Rossi, this test will be very important mentally. Both men arrive with great expectations of 2015, and being fast from the start will be crucial. Rossi has openly spoken of targeting a tenth world title, something which in previous years he has downplayed. A very strong 2014 sees him highly motivated, and fit, after a winter of dirt tracking at his won ranch. He starts 2015 off on a better foot than last year, now that crew chief Silvano Galbusera has a year of experience under his belt. The two have worked together well, and so Rossi will want to set down a marker right from the start.

Sepang will be even more crucial for Jorge Lorenzo. The first Sepang test of 2014 was the first blow in what became a long and painful series of beatings during the first half of the season, Lorenzo only fully finding his form in the second half of the year. The double world champion has learned from his mistakes, however: he has trained hard over the winter, and will arrive much lighter than last year, and in significantly better shape. He has nothing to fear from changes to the rules or to the tires this year, and is determined to make amends. He will want to be fast right out of the gate, and stamp his authority on the season from the start.

Over in the Monster Tech 3 Yamaha garage, Bradley Smith and Pol Espargaro will have less work to do on parts. Tech 3 will start the year on a bike not too far off the one ridden by the Movistar Yamaha men, but with less to test, their work will focus on set up.

That, too, is crucial. For Smith especially, as the Englishman was often fast during 2014, but rarely consistent enough to capitalize on it. He and his crew occasionally ended up chasing down dead ends with set up, forced to change their approach late in the weekend. Finding a strong base set up will be key for Smith, if he is to have a chance of retaining his ride at the end of this season.

Pol Espargaro will also be looking for consistency, after a very strong rookie year. He ended the season in sixth spot, and will be looking for a place in the top five in 2015. His problem is that so will everyone else, not least the Ducatis, and Cal Crutchlow and Scott Redding on the satellite Hondas. It will be interesting to see what Espargaro tests at Sepang: at a number of races in 2014, Yamaha allowed Espargaro to try to find a way of using his Moto2 braking style in MotoGP, sliding the rear to help slow the bike down. Sepang is a good place to try out new ideas in this area, as it has two corners with hard braking in a straight line from high speed. Definitely worth watching.

Honda

Development at Honda continues as ever, but their main area of concern is not performance, but rideability. The Honda RC213V is competitive – two triple crowns (rider, team and manufacturer championship) in two years is proof of that – but it is not easy to get the final few percent out of the bike. The RC213V is harsh and aggressive. At Valencia, HRC boss Shuhei Nakamoto pinpointed making the bike easier to ride his main priority.

Even Marc Márquez complained that the bike he tested in Valencia was too aggressive, saying that he found the way it locked the rear on corner entry too difficult to handle. With Casey Stoner having done three days of testing at Sepang last week, with HRC electronics people prominent in the photo, it is clear that this is one area they will have been working on. In a very rare interview, Stoner told the MotoGP.com website that they had been testing engine braking settings and engine mapping, as well as a few things with the front forks. All these should help make the bike a little easier to use.

While the goal for Marc Márquez is fairly straightforward – get back up to speed, ready to defend his title and shake off the poor second half of the 2014 season – his teammate Dani Pedrosa faces a bigger challenge. Despite being fit all year, Pedrosa had one of his least successful season, and needs to get back to winning races again. He has a new crew chief in Ramon Aurin, though a familiar one, as Aurin was previously his data engineer. That should make working together a lot easier, and Pedrosa and his new crew should be up to speed quite quickly.

If the test is important for the factory Hondas, for the satellite riders, it is absolutely crucial. Both Cal Crutchlow and Scott Redding were surprised at how hard it was to adapt to the RC213V at their first test on the bike at Valencia. Crutchlow was surprised at how difficult the bike was, while Scott Redding labeled the gap between himself and the front runners as 'unacceptable'. The two men will have to spend a lot of time on track just trying to understand the Honda, and trying to cut the gap to the leaders. They will not necessarily have to be within a few thousandths of Marc Márquez or Valentino Rossi, but they will have to reduce the gap from eight tenths (for Crutchlow) and 1.6 seconds (for Redding) down to just a couple of tenths of a second. What both Crutchlow and Redding will be looking for is progress.

Both men have new crew chiefs, Crutchlow forced to leave Daniele Romagnoli behind when he joined the LCR Honda team, and Redding back with the Marc VDS team, but without his former crew chief Pete Benson. In his place comes Chris Pike, formerly crew chief to Jonathan Rea in World Superbikes, and having had a winter to go over his notes and learn his way around an RC213V, Pike should be in good shape to help Redding on his way.

Ducati

As the bike we all wanted to see at Sepang will not be ready, we will have to instead try and decipher Ducati's intentions from the bike they will be bringing for the Andrea Dovizioso and Andrea Iannone to ride. Dubbed the GP14.3, the Desmosedici the Italian duo will be riding is a further evolution of the GP14.2 then finished the season on, but using last year's engine. As the engine is the limiting factor – too long, too large, and with major components in the wrong place – the chassis has been reworked to test out some of the principles which will be used on the GP15, and provide input into the development of that bike.

It will be interesting to see what changes Ducati have been able to make. What we know about the GP15 is that it will look broadly similar to the GP14.2, but smaller, and with a revised tail section and exhaust. As the GP14.3 will use the same engine as the GP14.2, it can't be too much smaller, but perhaps a new chassis will allow the tail section, and more importantly, a different weight balance. That could give valuable data on how turn in is affected, and offer more clues for helping to solve the understeer the bike is cursed by.

The engine layout cannot be altered – that is the task which Ducati have undertaken with the GP15 – there may be a chance for Ducati to modify some of the internals. The Italian magazine Motosprint wrote earlier this year that Ducati had tried increasing the weight of the crankshaft in 2014, looking for a more tractable engine manner. It stands to reason that if the engine internals of the GP15 are radically different to the GP14.2, properties such as crank weight and camshaft timing could be altered to emulate the GP15.

Andrea Dovizioso's main task at Sepang is to remain patient, and continue the excellent work he has done of analyzing the behavior of the Ducati and helping to improve it. Dovizioso knows he has to be patient, though after two years, Ducati really needs to deliver. The arrival of Gigi Dall'Igna at Ducati gave Dovizioso a badly needed boost, and he must hold that thought until the new bike arrives.

For Andrea Iannone, his main objective is to continue learning his way around the factory Ducati garage. The Italian performed well in the Pramac team, and was happy and fast, though he lacked a little consistency. Being a factory rider places more of a burden on a rider, and that is the load which Iannone must learn to bear.

Over in the Pramac garage, with Yonny Hernandez absent, the team can concentrate on Danilo Petrucci. He has adapted well so far to the switch to Ducati, at Sepang, he must continue this work.

Suzuki

There will be much attention paid to the newcomers at Sepang. Of the two new manufacturers, Suzuki face the highest expectations. Aleix Espargaro and Maverick Viñales both performed well at the Valencia test, with both riders praising the handling of the bike. It turned well and handled exceptionally.

The only problem was that it did not have the go to match the turning. The bike was well down on horsepower, considerably slower along the straight than the other factory bikes. That slower speed was partly intentional, the power having been dialed back a little after Randy De Puniet blew up a couple of engines during the race weekend. More engine failures followed at the test in Jerez later in November last year.

That is the problem which Suzuki have to fix. At Valencia, they told reporters they were confident they had found the cause of the problem, but may not be simple to test. The problem had not shown up on the dyno, so testing a fix on the dyno could be hard. Some of the paddock's smarter minds felt the problem Suzuki had was related to oil supply being affected by bike attitude. We will only really know if the problem has been fixed if Espargaro and Viñales make it through the test with the engines they use still intact.

Aprilia

What can we expect of Aprilia? It is hard to say. Give that they decided to return to MotoGP late in the season, they have not yet had too much time to work on the bike. At Valencia, the Aprilia ART was still slow, Alvaro Bautista 1.8 seconds off the pace, Marco Melandri an alarming 3.3 seconds behind the quickest man Márquez.

According to an interview which Alvaro Bautista gave to the MotoGP.com website, the main problem at Valencia was a lack of power, which was solved with a new engine which Aprilia brought to a test at Jerez later that year. The new engine – now with an 81mm bore and pneumatic valves – had a lot more power, but was starting to run into the limits of the chassis, and needed a lot more work done on the electronics to manage the power. Aprilia's test rider Max Biaggi spent the World Superbike test at Jerez testing the factory's MotoGP electronics, and so the package which Aprilia bring to Sepang should be more competitive.

It will still be tough, though, as Sepang is a much, much faster track than Valencia was. Even if Aprilia has closed the gap to Honda, Yamaha and Ducati, they could still find themselves a long way behind the leaders. Two long straights really can kill lap times.

As for the riders, Alvaro Bautista starts the season exceptionally motivated, after having felt like the fifth wheel on the wagon at Gresini Honda. Now a factory rider again, and with the resources of the factory behind him, he can start to push to develop the bike, and to try to score results. His own performance in 2014 will be his first target, and a measure of progress for Aprilia.

On the other side of the garage, Marco Melandri faces an uphill task. Melandri was a reluctant convert to MotoGP, having been happy fighting for the title in World Superbikes. Melandri has some challenges in getting reacquainted with MotoGP and the Bridgestone tires, but his main objective must be to find real motivation again from within himself.

Open Bikes

And what of the Open bikes? For the Honda riders, they now face MotoGP with a bike which at least has some horsepower. The RC213V-RS, the replacement for the underpowered RCV1000R, is much closer in performance to the factory bikes than the production racer ever could be. But added power means more work on set up, and more work for the teams and Magneti Marelli to do on making the bike easier to ride fast.

Rookie Jack Miller has perhaps the easiest task: with a three-year contract with HRC, he has little pressure on him. His goal is to learn, to adapt, to get used to riding the bike, and try not to get carried away in the process. The first test at Sepang is another step on that path for the Australian.

Nicky Hayden faces a much stiffer test. The American was sorely disappointed by the performance of the RCV1000R, and also spent the year struggling with a wrist injury, then missed races to have surgery on the wrist. Though the radical surgery – removing a row of bones in his wrist – brought a big improvement, he still lacked some motion in his right wrist, and he will be hoping that therapy over the winter will have brought some of that back. If Hayden does not have a good season in 2015, that could mean a lack of Americans in the MotoGP paddock from 2016.

At Forward Yamaha, all the pressure is on Stefan Bradl. The German had a solid couple of years at LCR Honda, then went backwards in 2014. He needs to reverse that trend, and a change of bikes may help. What results he needs to achieve is hard to say, but clearly, the times of Aleix Espargaro will serve as a guideline.

Bradl at first feared he would be lumbered with Kayaba suspension, after Forward agreed a deal for the Japanese suspension firm to supply forks and shocks. But after a disastrous first test at Valencia, Bradl made it clear that he would not work with the firm. The Kayaba adventure now looks to be past, with Forward having switched back to Ohlins.