Adrian Sutil has said that it is frustrating that Sauber has not been able to get on top of the problems affecting its 2014 F1 machine but acknowledges that it is working constantly in search of improvements.

The German driver is one of seven - along with team-mate Esteban Gutierrez - yet to put a point on the board this season. While the quartet at Caterham and Marussia are maybe not expected to have breached the top ten, Sauber's proud tradition of being a feisty midfielder capable of occasionally upsetting the big guns is taking a bit of a battering as unreliability and unpredictable handling make life hard for the drivers.

"We have a problem with the aerodynamics, especially in the corner, so whenever there is a corner coming, [the car] is not doing the right thing," he explained to journalists on the eve of practice for the Monaco Grand Prix, "It is unpredictable at the moment.

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"To be honest, after the first two tests, I thought it is going to be a hard start [to the season]. You always try to think in a positive way, but I had a few worries before the first race - we were not ready and the car, from a driveability point of view, was not where it should have been. You could see it in Bahrain in testing, but it's where we are at the moment and we have to improve and make it better. It is one of the most difficult starts [to a season]."

Like its rivals, Sauber brought a raft of developments to Barcelona for the Spanish Grand Prix and ensuing in-season test, but quickly realised that it still had a lot of work to do.

"The update in Spain didn't really work," Sutil confirmed, "The only thing that did work was the weight reduction. The feeling on a single lap, or quali lap, was better, and [we moved] closer to Toro Rosso and Force India, but to recreate it all the time, when we needed it, in the race, was a bit difficult, especially in Barcelona where we went a bit wrong with the tyre pressures here and there."

From a strong midfield points contender, Sauber has been reduced to a near also-ran following F1's major rules overhaul, and Sutil admits that the team is struggling to come to grips with the handling issue.

"The driveability of the car is quite poor, but I think we made some good promising changes in the test. The team understands why Barcelona wasn't any better, and me too, so this is the first step - and the next step is to change it, make it better. We have something on the car which should help for this weekend, but I don't want to say too much....

"Every day there is an improvement, every day we are on circuit we learn, but it shows me just how much we have to learn with the new car - we are really in an area with no experience at all. There are times in the race where you can't control it - you go from tricky to driveable to undriveable, locking up front and rear, understeer, oversteer... This is the worst thing you can have when you don't know how to solve a problem, just shift it from one end to the other. It comes from a loss of grip when you enter a corner, so it might be somewhere else that we have to look - maybe the brake system is doing the right thing, but we just haven't got enough grip and then you don't feel comfortable in the car if it keeps moving around on braking."

The former Force India driver - who must be regretting moving in the opposite direction to former Sauber pilot Nico Hulkenberg for 2014 - is also still concerned by the weight of the C33 and also the tyres that Pirelli have provided so far this season.

"[The weight of the car] is still a bit too much for my weight situation, but we've reduced it quite a lot," he noted, "From Bahrain to Barcelona, we had a good step in terms of weight reduction, but I am still heavier. Esteban is fine but I'm still on a diet!

"From Bahrain to here, [the car has shed] maybe 10kg, which is 3-4/10ths, but there's still a bit more that we have to find. I think the best situation is when you have 5kg to play with, so then you can place it where you need it, but we still need to wait a little bit longer [to be in that position].

"I also think Pirelli are much too conservative, especially as last year we had much faster cars. In a way, we probably needed a harder tyre [then], and now we need a softer tyre, but they've made it the other way around. I'd like to have a bit softer tyres as you could see during the test in Barcelona how much faster they were. There was an improvement of around two seconds just in the tyres and this is the time we were missing to be able to say it was enjoyable to drive [an F1 car]. In Barcelona, it was difficult to get that F1 feeling as the car was too slow and had no grip."

With Monaco providing a very different challenge to the Circuit de Catalunya, however, Sutil is in a slightly more positive frame of mind for the coming weekend.

"Here it is a very different circuit," he agreed, "The corners are very slow, so it's not all about the aero. If the car is set up mechanically quite well, you can get around here. I think it's a very special place, a very special race, with a lot of opportunity for small teams like us. You never know in Monaco....

"I'm much more confident than I was. It's just finding a small little adjustment here and there and suddenly your confidence increases, degradation on the tyres goes down and you are so much more competitive. I think we have done some modification [for Monaco] and need to see how it goes, but we haven't solved all the problems, that's for sure."