He insists then are capable of coming back from their 4-0 Bernabeu hammering.
Mabbutt told the Daily Star Sunday: "They must stay positive."
Ex-England defender Mabbutt cited how Spanish giants Real came back from a Euro thrashing and still went on to lift the UEFA Cup 25 years ago.
"Realistically we know it's going to be an uphill task," explained Mabbutt.
"But you never know in this game, especially with an early goal or two.
"Real themselves showed how you never say never, when they lost 5-1 to Borussia Monchengladbach in 1985 and then won 4-0 in the second leg of the quarter-finals before winning the trophy.
It's a huge target but no one at Spurs will have given up in the slightest. The team's got a great attitude."