Ex-Chelsea boss Gianluca Vialli has told his old club Andriy Shevchenko will come good - amid reports the Blues want to offload the £30m striker.
Shevchenko has just three league goals so far
Reports on Tuesday said Valencia's David Villa could be a £22m replacement for the out-of-form Shevchenko.
"I think it is quite normal when you are coming from a different country," Vialli told BBC Sport.
"I think we will soon see one of the world's top strikers in the Premiership - there are no worries about that."
Despite the reports linking Villa with a switch to Stamford Bridge, Valencia president Juan Soler insists Chelsea will have to offer £100m to prize the Spaniard away from the Mestalla Stadium.
Soler said: "Officially we have not received any interest or an offer from Chelsea for Villa.
"We have no intention of selling him. But should any club be interested, they could sit down and negotiate his buy-out clause, which is currently worth £100m."
Shevchenko has struggled to find his form since his move from Serie A, but Vialli is confident he can revive his Chelsea career.
Vialli made the move from Italy to England when he joined Chelsea from Juventus for £12m in 1996.
He believes Shevchenko, who has scored just three league goals this season, has been hampered by the knee injury that threatened to force him out of the World Cup.
Vialli added: "He played in Italy and had to adjust to the Italian style and now he must adjust to the English style.
"When he joined I don't think he was 100% fit, he was injured before the World Cup and he only had a very short break.
"All of these things catch up on you and you need time to get back to your best. But I think Shevchenko is working really hard."
Vialli believes Shevchenko's presence in the side has been of great benefit to strike partner Didier Drogba.
He said: "Drogba is playing so well and scoring some marvellous goals. I think this is down to him but also what Shevchenko is doing in keeping two or three defenders busy.
"It means Drogba is given more space and more ability to score. As a partnership they are working really well together and working hard for each other.
"And I don't see any jealousy which is very good for the team."
Michael Ballack, who also made a much-hyped move to Chelsea from Bayern Munich during the summer, has also not had the instant impact on the side that was expected.
But Vialli feels the German skipper has shown himself to be a real team player since arriving at Stamford Bridge.
Ballack (left) failed to shine in the 1-1 draw with Man Utd
He said: "Ballack is a very good player and I think he is doing his job for Chelsea, but when you play with so many great players it is difficult to be at the centre of attention.
"He might do things very well but it gets lost because Frank Lampard has an amazing game or John Terry is fantastic, so you have to be part of the team and this is what him and Shevchenko are doing at the moment."
Vialli has been out of management since a short spell with Watford was ended with his sacking in 2002.
He has co-authored a book, The Italian Job, which was nominated for the Sports Book of the Year award and also works as a pundit on Italian TV.
"I'm happy what I'm doing and I'm in no hurry to make a comeback," he said. "At the moment I'm not in the market.
"But if the right opportunity comes up I will think about it and perhaps take it."
Vialli has previously spoken about his destiny of one day returning to Chelsea, who he led to FA Cup, League Cup and Cup Winners' Cup victories.
"I would love that but Mourinho is doing a great job," he said. "He is possibly the best manager in the world, along with a few other names.
"To manage this team would be a dream come true but I don't see it happening. But if they call me I'm available!"