Sauber is braced for a difficult few races until a major upgrade package arrives in time for the Belgian Grand Prix later this summer.

Sauber started the season brightly, with Felipe Nasr claiming fifth on his debut in Australia while Marcus Ericsson backed up that result with his first Formula 1 points by placing eighth.

Further points followed at the Chinese Grand Prix but since that race they have scored points only once, courtesy of Nasr's ninth place result in Monaco.

Following its point-less campaign in 2014 as it slipped to 10th in the Constructors' championship, its current placing of sixth with 21 points is a vast improvement, though the C34 remains fundamentally the same car it was in Australia, with a major upgrade package - both chassis and on the engine side from Ferrari - not set to be introduced until the Belgian Grand Prix.

"It’s difficult," Nasr said when asked by F1Zone.net if Sauber was playing a waiting game until the Belgian Grand Prix.

"I’d say I’m looking forward to those updates to come as soon as they can, but I’m not going to be upbeat by the result in Canada, we have to keep on working always to improve ourselves."

Ericsson was more upbeat, pointing out that Sauber was still within touch of Q3 in Canada.

"We still need to fight and we are not that far off as we showed in qualifying, we were two-and-a-half tenths off Q3 so we are there or thereabouts," he emphasised.

"We need to improve the race pace as that was disappointing but then also not many people retired, a clean race, we cannot just wait for [the planned] upgrades as we need to take opportunities that present themselves as there’ll be races where we get opportunities as we need to of course analyse this but not be too negative and we need to take opportunities we can get."

The Canadian Grand Prix was disappointing for Sauber as both Ericsson and Nasr expected the Circuit Gilles Villeneuve to play to the strengths of the C34. With Ericsson 14th and Nasr only 16th, the pair attempted to explain what went wrong.

"Looking back at the race we did everything right with strategy, the driving, the balance of the car but we just lacked pace – as simple as that," said the Swede.

"It’s quite obvious that we’ve lost a bit compared to our competitors the last couple of races and we are lacking a bit of pace in general. We need more grip and lap time to be able to fight higher up. I could not have done anything better, the balance was good but we are not quick enough."

"We had a lot of braking combined with having to ride the kerbs a lot plus good traction and we saw we were weak in these areas," explained Nasr.

"Riding the kerbs and traction for me was not good at all. When I was racing other cars I could feel we were lacking a lot of those areas, but we did expect other things so that’s why we are all a bit surprised by the outcome, but [we have] more things to analyse and work on, that’s how it goes, you need some bad weekends for the team to analyse what went wrong to improve it for next time, this is part of the process."

With Lotus having appeared to overcome its early problems and Force India set to introduce its B-spec car next week, Sauber must try and take advantage of any opportunities which come its way if it is to remain in the midfield hunt. The Swiss team can only hope that its promised upgrade package arrives on time in Belgium and delivers the required step forwards in performance.