Trials can often be a tribulation for NRL coaches - a necessary evil. They're needed because each team wants to have a hit-out or two before the start of the regular season but if players get injured, then they're often considered a waste of time.

Here's a look at what the 16 NRL coaches will want to see through the trial period over the next fortnight.

Brisbane Broncos

With discussion around Corey Oates moving to the pack and star recruit Jack Bird out with a shoulder injury, the pre-season will give coach Wayne Bennett plenty of chances to assess how the likes of Jamayne Isaako, Jonus Pearson, Tom Opacic and Gehamat Shibasaki cope with those centre and wing spots.

Skipper Darius Boyd (hamstring) is unlikely to feature much if at all in the trials. If Oates does earn a spot in the pack it means frontrunner Isaako and at least one of the other up-and-comers will need to join James Roberts, Jordan Kahu and Boyd in the back five.

The trials will also be a chance for playmakers Troy Dargan (halves) and Todd Murphy (half/hooker) to press their claims for Kodi Nikorima's No.7 jersey and at hooker with Andrew McCullough racing the clock for round one.

Canberra Raiders

Other than the hooking duel between recruits Siliva Havili and Craig Garvey (and a possible halfback challenge from the returning Sam Williams, which could even potentially force Blake Austin into dummy half), most spots in the line-up look reasonably settled. The more pressing question for coach Ricky Stuart is how to address his team's backwards move last season after their impressive 2016.

The numbers suggest they weren't overly adventurous - last for total passes and total kicks across the regular season, as well as last for total support and decoy runs and 13th for run metres gained. The real shocking stat for Stuart's squad was a whopping nine losses by six points or fewer (easily the most of any team in 2017); they needed just two more wins to have played finals.

That issue is tough to correct in the low-intensity environment of trials but finding the mental grit to consistently close out close games will be top of the club's to-do list.

Canterbury Bulldogs

The Bulldogs have gone through as much off-season change as any side and will be a drastically different team in 2018 under new coach Dean Pay, who will be looking to the trials for plenty of answers. In particular he'll like to see some positive signs that Moses Mbye will handle the shift to fullback.

He'll also want Matt Frawley, Nu Brown and Josh Cleeland to demand a spot in the halves alongside Kieran Foran, who needs to get a few miles in before round one with the star Kiwi still on restricted duties coming back from injury.

It's no secret the Dogs' biggest problem in 2017 was an inability to score points – they finished last for points, tries and line breaks. So while the first focus for every side (especially in the pre-season) is getting their defence in order, Pay will also be keen to see a few attacking sparks from the overhauled playmaking structure.

Cronulla Sharks

For Shane Flanagan's men the big question is how quickly former Penrith Panthers fullback Matt Moylan can feel at home in James Maloney's vacated No.6 jersey. While Moylan is an experienced first-grader with 89 appearances, he has played just eight of those at five-eighth. The early signs are good though with Penrith winning six of those eight (all at the back end of 2017) while Moylan also has a win in his one game there at Origin level.

Maloney also leaves a gulf in terms of goal-kicking so expect Val Holmes (career goal-kicking average 72%), Moylan (62%) and Dugan (56%) to each pot a few attempts through the pre-season. The acquisition of Trent Hodkinson late in the pre-season is an interesting one – if he plays he would immediately fill the goal-kicking gulf but if he starts in the halves does that force Moylan back to fullback (and Holmes to wing) or put pressure on Chad Townsend to stay in first grade?

Gold Coast Titans

After a horror 15th-place finish to an injury-ravaged season, the Titans will be desperate to hit the ground running. The team hasn't undergone major surgery in the play-making positions – veteran Michael Gordon should slot in seamlessly at fullback – but there is huge pressure on five-eighth Kane Elgey to improve.

New coach Garth Brennan isn't spoiled for choice in the position but up-and-comer AJ Brimson will be looking to pressure Elgey for a spot.

Structure-wise – it's no secret the Titans leaked a ton of points in 2017 but their left edge was particularly sieve-like (Dale Copley's 30 total try-causes were the most in the NRL). Given Anthony Don's injury it's possible new centre Brenko Lee will push Copley out to a wing.

Brennan also needs to see some positive signs out of new recruit Bryce Cartwright, who could provide some much-needed spark if he rediscovers his best form.

Manly Warringah Sea Eagles

Manly shrugged off a horror 2016 to exceed the expectations of most last year. A key part of that was Blake Green providing an ideal foil for Daly Cherry-Evans. His departure leaves a big gap and the most logical replacements – short of adding another playmaker to the roster – are Jackson Hastings and former Raiders young gun Lachie Croker. Hastings showed his undeniable talent when thrust into first grade at the Roosters at an early age but he seems to be struggling to impress coach Trent Barrett. Croker, a former NSW and Australia under-20s rep, has the inside running after blitzing the pre-season but is still very inexperienced.

The five-eighth conundrum isn't just the big question for Manly, it's almost the only question and will make or break their season so they need to get it right early on.

Melbourne Storm

The Storm's main question is who will wear Cooper Cronk's old No.7 jersey and partner Cameron Munster. Cronk clone Brodie Croft is the hot tip but Ryley Jacks has done well in his limited chances and uncapped pair Billy Walters and Scott Drinkwater are in the conversation.

Whoever gets the nod will have a huge head-start on the halves feeling their way at other clubs: the chance to learn from and partner with the greatest No.1 and No.9 of the modern (or, arguably, any) era in Billy Slater and Cam Smith, plus one of the best coaches in the business in Craig Bellamy.

Croft and Jacks in particular have been in the Storm system long enough that they should be able to slot into the defensive structures almost instantly. Melbourne's three-week trial schedule includes a big World Club Challenge match against Leeds giving them plenty of time to settle on combinations.

Newcastle Knights

We probably could've written this whole article just on what Knights coach Nathan Brown will be hoping to get out of the pre-season with his drastically overhauled squad.

Potentially three of four names in the playmaking spine (assuming Connor Watson holds out Brock Lamb in the race to partner Mitch Pearce) will be recruits with fullback Kalyn Ponga and Pearce at No.7 sure-fire starters.

A mountain of experience joins the forwards and in total eight of NRL.com's predicted 17 for round one are new signings. Needless to say Brown will be putting the trial period to full use trying to build combinations and iron out any kinks but realistically it will take at least a few rounds of the season proper to really start to click.

Probably the biggest thing Brown will want to see through the trials is the incoming senior players like Pearce, Jacob Lillyman and Chris Heighington leading the way, helping develop the younger players and putting their stamp of professionalism on things. Four of the new faces are premiership winners so instilling that belief and winning culture is arguably even more important than combinations early on.

North Queensland Cowboys

Things couldn't be looking much brighter for Paul Green's men.

They made the 2017 Telstra Premiership decider with two of their best players sidelined with injury. Not only do they welcome back Johnathan Thurston and Matt Scott along with star recruit, Kangaroos prop Jordan McLean, but Thurston's halves partner Michael Morgan matured out of sight as a player in Thurston's absence last year.

The squad is actually still remarkably similar to the one that won the 2015 grand final. Green knows they can all play, and play together.

With a few of his most prized players heading towards the end of their careers, the main thing the Cowboys want to see from the trials is all their stars emerging fit and in form. Tick that box and they could well go on an early-season tear.

Parramatta Eels

The Eels' phenomenal depth means they bat deeper than arguably any other club and will quite possibly have the most NRL-calibre players outside their game day 17 in any given week, meaning tons of competition for spots in the pre-season.

One of the biggest questions is how the returning Jarryd Hayne fits into a team that has evolved dramatically in his three years away. While he could take over from Semi Radradra at left wing, a move to the centres looks more likely as Brad Takairangi migrates into the back-row rotation. With some unwelcome headlines very early on in his return, Hayne – and the Eels – will mostly be hoping to see him get through the rest of the pre-season controversy-free.

Penrith Panthers

Another team, another new halves combination. This one shouldn't take much work though – Nathan Cleary is already an established NRL halfback and James Maloney shapes as the perfect foil at No.6. Given Cleary has never had an established half alongside him (barring one game – his NRL debut – alongside Jamie Soward) he should take to this like a duck to water.

The team also needs to work out how best to use Tyrone Peachey – in what shapes as his final season at the club – to get the best out of him. His dynamic attack at centre is offset somewhat by some defensive weaknesses and he may best be utilised as a bench impact player.

South Sydney Rabbitohs

All the Bunnies really want to see through the pre-season is their talismanic skipper Greg Inglis back to full fitness and in form. Roughly 10 months on from an ACL injury that ruined his 2017 season, Inglis is inching towards a playing return and new coach Anthony Seibold will hope to put a few kilometres into the 31-year-old's legs before the season proper in hopes he can hit the ground running at fullback.

Failing that, Inglis may need to be managed into the season (potentially starting off in a lower-impact role at centre) which is less than ideal.

Something else the team needs to brush up on – and Inglis will be a massive help here – is defending kicks. The Bunnies conceded 33 tries from failing to defend kicks last season which was equal-worst alongside Canterbury.

St George Illawarra Dragons

Aside from the obvious item on the wish-list – new halfback Ben Hunt and likely fullback Matt Dufty gelling with skipper Gareth Widdop and hooker Cam McInnes – Paul McGregor needs to sort out the huge drop-off his team suffered in the second half of last season.

Splitting their season into the first 13 rounds (an 8-4 winning record, average points scored 23.75 and conceded 16.25) and last 13 rounds (a reversed 4-8 record, just 20.66 points scored per game and 21.25 conceded) shows a massive plunge in both attacking and defensive effectiveness.

Their tackle efficiency dropped from 89% to 86% and total dominant tackles dropped from 80 to 23. It's a tough one to fix in the pre-season but the work done now should carry through not just the first half of 2018 but right through the finals, should they get there.

Sydney Roosters

Another club, another new halves combo. Like Maloney at Penrith, Cronk at the Roosters provides a stable and experienced foil for his younger partner and star fullback James Tedesco is another who should hit the ground running easily.

Of more concern to coach Trent Robinson is the club's thinned goal-kicking stocks following the departure of Michael Gordon.

Sio Siua Taukeiaho (career average 77%) looks the best option but rarely plays the full 80 minutes and spent the second half of 2017 coming off the bench. Latrell Mitchell (62%) should play 80 minutes every week but is far less consistent off the tee.

Nobody else in the frame for a round one spot has ever kicked a goal at NRL level. Taukeiaho should start the season in the run-on side as preferred kicker.

Warriors

One of the most perennially frustrating teams for supporters, the Warriors are again a side brimming with talent – but it didn't help them much in 2017 as they slumped to a 13th-place finish.

New five-eighth Blake Green will need to do for Shaun Johnson what he did for Daly Cherry-Evans at Manly last year and provide a steady foil, calm head and deft kicking game to allow his high-profile halves partner to excel.

Aside from the new combinations, coach Steve Kearney may want to have a look at the Warriors' conservative style, which back-fired last season. Although they had the fewest incomplete sets of any club, made the second-fewest total errors and conceded the fifth-fewest penalties, they also finished third-last for offloads and fourth-last for points scored, indicating a return to a slightly more expansive play would be beneficial.

Defensive structures will be critical as they always are to any team in the pre-season but the trials will present a perfect chance to see how the Warriors go if they chance their arm a little more too.

Wests Tigers

The halves partnership between Luke Brooks and former Bulldogs fan favourite Josh Reynolds is just the start of the list of questions for Ivan Cleary.

Perennial utility Tuimoala Lolohea needs to stake a claim on James Tedesco's old No.1 jersey (after performing admirably in the halves last season) as well as either incumbent Matt McIlwrick or young gun Jacob Liddle (who missed much of 2017 injured) to put their stamp on the dummy-half role. McIlwrick will get a head-start with Liddle still on the injured list through the trial period.

There are a raft of backline options with at least six players vying for probably two centre and wing spots and those questions will also need to be answered in the trials. Even in the pack there will be three or four players very unlucky to miss out come round one.