Lotus F1 owner Gerard Lopez believes Kimi Raikkonen's enthusiasm and desire coupled with freedom from the team has helped the Finn to blossom.
When the Enstone squad decided to lure Raikkonen out of the retirement, many questioned whether he would be motivated following a few years in the World Rally Championship.
However, the former World Champion impressed during his comeback season as he finished third behind Sebastian Vettel and Fernado Alonso in the standings and also claimed one race win and six further podiums.
In an interview with Gazzetta dello Sport Lopez said: "Everyone who had claimed that he wasn't motivated now comes around to tell me they knew Kimi was still super strong.
"It makes me smile. I knew it would be like this. Raikkonen has put in a great amount of work to compliment his talent and the results are the fruit of that."
He added: "He feels like he is used for what's most important and the rest of the time he is free. He's found a balance; we speak every week and he feels good. He has enthusiasm and desire. I want drivers, not robots."
Raikkonen's team-mate Romain Grosjean endured a mixed season as he claimed three podiums but found himself in the stewards' office more often than not.
He was eventually slapped with a one-race ban for his role in the first-lap carnage at the Belgian Grand Prix, but Lopez feels the Frenchman wasn't as bad as some people claimed he was.
"There were four drivers who had more reprimands than him, but they took part in every race and Grosjean was instead banned for the Italian Grand Prix," he added. "However, he has shown that he is quick - I'm expecting a lot from him this year."
