The striker has been troubled with a groin problem since the World Cup finals and aggravated it during the 3-2 first leg defeat in Switzerland last week.
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Surgery could rule Defoe out for up to a month, but Spurs boss Harry Redknapp will delay any operation until after Wednesday’s match at White Hart Lane.
Defoe will definitely miss England’s forthcoming Euro 2012 qualifiers, but will play through the pain barrier as Spurs bid to qualify for the Champions League group stages for the first time.
Redknapp told the BBC: “It might only be half a game he can last now, but its getting less each time. The pain is getting worse.
“He wants to play and train all the time but he’s got to have it done now. He can’t go on like that.
“He has not trained a lot. When he has trained, he’s been all right, he’s been sticking goals in.
“But then he’s had days off where he couldn’t train and he’s getting worse all the time. 60 minutes is about as much as he can last.”
Tottenham will definitely be without Luca Modric at White Hart Lane.
The Croatian midfielder also strained his groin after last week’s first match in Switzerland and will not be risked.
The North London club, who like Young Boys are trying to qualify for the Champions League for the first time, hit back from 3-0 down in Berne to give themselves a fighting chance of reaching the lucrative group stage.
Redknapp hopes to have strikers Robbie Keane and Roman Pavlyuchenko, scorer of his side's second goal in Switzerland, available after they also missed Saturday's 2-1 Premier League win at Stoke City.
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