Ajax got a draw versus Benfica by 2-2 yesterday and they could have defeated Benfica too in fact. But I still don't think that this will cause a serious trouble for them in the second leg. I have zero expectation like Ajax would have a hard time destroying Benfica home. Benfica did a good job in Portugal and resisted them. But they can't do the same thing by the same effort to Ajax again. Ajax would demolish Benfica like they did to Sporting in the group stage of the tournament.
They took the lead quite convincingly early in the first half which made them relax a bit but this had a pretty bad impact because gradually Benfica found their rhythm in the game which made them play better from the first half. And as a result, they scored 2 goals in return.
This is clearly a loss for Ajax even though they are playing at home but still it is very bad when they can actually maintain the advantage