An increasingly desperate Felipe Massa has once again pleaded his case to remain with Williams in 2018, following tests for Robert Kubica and Paul di Resta at Silverstone earlier this week.

The Brazilian's future with the team is looking increasingly insecure as the British outfit weighs up their alternatives for next season. Though no word was given on Di Resta's outing, the interest around the potential comeback of Kubica led Williams to describe his run on Wednesday as "successful" when asked for comment.

However, for the 37-year-old Massa, he insists the dynamic he has forged with young teammate Lance Stroll is enough to warrant his retention warning of difficulties should they replace him.

"It's frustrating that the team is trying to go in a direction that can really be much worse than keeping the same," he claimed. "If you see Lance is growing a lot, so, to be honest, I'm really doing a great job with my driving.

"I think the team has a direction that can just be positive to keep the way it is. If the team changes something, they can pay more than it costs to keep me! The team knows 100% what I am able to do."

Speculation has arisen that Kubica, a former Grand Prix winner before his career-changing rally crash in early 2011, brings not only the talent he possessed in his first career but also significant financial backing from his native Poland.

Previously, the 2008 championship runner-up has claimed he has those "who know about motorsport" behind him at Williams but concedes the decision may not be purely based on skill.

"I really like Paddy, and Paddy knows what is better for the team," Massa said referring to Technical Director Paddy Lowe who joined from Mercedes earlier this year.

"Maybe it's not 100% his decision, and they have to make a decision related to some other stuff. Unfortunately money is part of this game, unfortunately not in the right way, for the professional drivers, for the professional teams.

"That's why I think if Williams keeps the direction they have now, they are behaving like a professional and top team. If not, they're thinking about different things.

Related Stories:

• Ecclestone backs Kubica for Williams seat in 2018
• Kubica completes Williams test at Silverstone
• Massa hints at division within Williams over 2018 seat

The situation is very different to 12 months ago when Massa was ready to step aside and retire from F1 only to come back in January to allow Valtteri Bottas to join Mercedes.

Explaining why the former Ferrari driver said: "I feel really comfortable driving this car. The car from this year for my driving style is a very good connection.

"The car from maybe the last three years, without the grip, just going sideways with the terrible tyres, is not a great pleasure and maybe for my driving style, I cannot give the best for different issues.

"Now I can, and maybe when you feel you are giving the best that you can give, then you are more motivated. So I still believe I can give, that's why I want to carry on."