Former F1 world champion Mika Hakkinen believes Mercedes constantly pulled the mat from underneath Valtteri Bottas that ate away at his self-confidence.
Bottas will lead Alfa Romeo into F1's new era this season after being overlooked by the Silver Arrows which has opted for George Russell to partner Lewis Hamilton.
Alongside Chinese rookie Guanyu Zhou, the Finn will instead look to rebuild a team that finished a lowly ninth in the constructors' championship last year.
Crucially for Bottas, he has been handed a long-term deal by Alfa Romeo, in stark contrast to Mercedes where he was on a rolling one-year contract.
Commenting on his compatriot's prospects for the forthcoming season which ushers in new regulations, Hakkinen told SuomiF1: "Valtteri is a great team player and driver.
"He's going to drive at a nice team. However, the resources of the teams [Mercedes to Alfa Romeo] are not comparable.
"Now, however, he can prepare for the long term. At Mercedes, with only a year-long contract, while light was always visible at the end of the tunnel, there was always a locked door waiting.
"That uncertainty eats away at self-confidence. He did not get the credit he wanted from Mercedes. If the mat is constantly pulled from under your feet, then it will eat your self-confidence.
"Now Valtteri has the opportunity to drive for a team for the long term where he will be trusted."