Seven-times Formula One world champion Lewis Hamilton defended Valtteri Bottas as an 'amazing team mate' on Thursday after the Finn faced questions about his future at Mercedes and the possibility of being replaced mid-season.

"I feel like we have the best line-up currently, in terms of the equilibrium that's within our team," Hamilton told reporters at the Spanish Grand Prix.

"At some stage it's going to change, I'm not going to be here forever, Valtteri won't be here forever but right now I think he's delivered time and time again over the years and he continues to.

"Valtteri qualified on pole last race. It's only the fourth race (this weekend). I think people need to give him a break and just let him focus on doing what he's doing," he added.

Bottas had earlier given short shrift to the speculation, with an additional dig at rivals Red Bull which has switched drivers repeatedly.

Mercedes team boss Toto Wolff recognised after last weekend's Portuguese Grand Prix that a sensor failure had hampered Bottas in the battle for second place in that race.

"We let him down with the engine that went into a safety mode," said Wolff in Portugal.

"Like many times it could have worked for Valtteri and we were pushing hard and continue to support him and see what he is capable of doing in Barcelona."