Petit, the French World Cup winner who also won the Premier League with Arsenal, feels Chelsea are not clinical enough and that will cost them in the final club game of the 2020/21 season.
While he has been impressed with Thomas Tuchel’s side defensively, he says they are guilty of missing too many opportunities.
City, by contrast, are more ruthless in front of goal and Petit thinks that will prove to be the difference in Porto.
‘When it comes to a final, and your whole season hangs on one game, you need to be clinical in both areas in front of goal,’ Petit told Paddy Power.
‘Defensively with Chelsea, that’s guaranteed. But up front I’m not so sure.
‘In a final you might get only two or three chances to score, and you need to take them. Chelsea have too many players who need four or five chances to score.
‘Manchester City have players who need only one chance. I don’t think there are going to be many chances in this game, so City are the better choice for me. That’s why I feel as though City are going to win this final.’
Petit singled out Phil Foden, Mason Mount and N’Golo Kante as three players who could have the biggest influence on the final.
‘Phil Foden and Mason Mount are the young game-changers who could hold the key to the destination of the Champions League trophy in Porto this weekend,’ he added.
‘I’ve been so impressed by both these players this season. We can all agree what a bright talent Manchester City have in Foden and, like Mount at Chelsea, he has a wonderful future.
‘Another man who could be key in the final is N’Golo Kante. If he is 100 per cent fit physically and mentally, he will cause big problems for City.
‘I’m very excited about seeing so many talented players on both teams and I’m hoping for very good final full of emotion between two English clubs.
‘I hope the best team wins but of course, as a former Chelsea player, I’d like to see them do it. It would represent a huge achievement for Thomas Tuchel and his team.’