Chelsea legend Kerry Dixon believes Andriy Shevchenko's fine display in the Champions League against Porto proves the striker is back to his best.
Shevchenko has finally started to impress Mourinho
Shevchenko's equaliser was his fifth goal in seven games and Dixon says the timing is perfect ahead of Sunday's Carling Cup final against Arsenal.
"We haven't seen the best of him but he played his best game so far and scored a great goal," Dixon told BBC Sport.
"He's a great, great player and I've no doubt he will be a big success."
Dixon - who scored 193 goals during his nine-year career at Stamford Bridge - laughs off talk that the Ukraine striker has been a failure following his £30.8m summer move from AC Milan.
"No, no, no," Dixon scoffs. "I wouldn't say that at all.
"Andriy Shevchenko is a world class player and things just haven't been going for him since he arrived at the club. But you can't write off a player like that.
"He has still worked hard for the team and has scored a few goals without being prolific - if he'd scored just five more goals people would be saying he'd had a good season goals wise."
And former England striker Dixon believes 30-year-old Shevchenko will not be the last big name player to find the going tough in England.
Shevchenko was world class before he arrived at Chelsea and nothing has changed
Dixon said: "A lot of foreign players have struggled to adapt to the English Premiership - you have only got to look at the likes of Didier Drogba and Thierry Henry who found it tough in the Premiership at first and have gone on to establish themselves.
"It's a different country, different tactics, different team-mates, different surroundings, and a completely different culture. He had to learn a new language - and it all takes time.
"You can't question his quality - he was world class before he arrived at Chelsea and nothing has changed."
Blues boss Jose Mourinho seemed to be far less understanding.
The Ukraine superstar has been left out at various times this season with Mourinho dropping none-too subtle hints that Shevchenko needed to do more to keep his place.
But the Premiership defeat against Liverpool - where Chelsea were completely outplayed - seems to have been the turning point for Shevchenko and he has responded to his coach's criticism with a series of impressive performances.
And Dixon, who combines working for Chelsea on match days with media work, also denied concerns that Shevchenko's arrival has caused major disruption.
Jose Mourinho's favoured 4-3-3 system - a system which has delivered two consecutive Premiership titles - has often been ditched in favour of 4-4-2 to accomodate Shevchenko but Dixon says that means nothing.
"I don't think the formation matters," he said. "Chelsea can play 4-4-2 and 4-3-3 and they both work. They have top players all over the pitch and can easily play in different styles - that's not a problem."