Tottenham Hotspur are into the FA Cup fourth round after beating Middlesbrough 2-1.
A comfortable win ended with a nervous final few minutes after Boro pulled a goal back.
He said: "Paulo Gazzaniga has got to do a lot better with the Middlesbrough goal.
"People talk about Jose Mourinho and clean sheets but you can't legislate for mistakes like that as a manager."
Hugo Lloris is still out injured and has been since October.
Jenas did have positive words for one Tottenham player, Japhet Tanganga.
The Spurs defender made his second successive start, this time at right-back.
Tanganga was a revelation in the role and Jenas said he was impressed with the 20-year-old's performance.
He said: "Japhet Tanganga had a couple of chances, it was a great display. He speaks really well, he's mature, he seems a real good prospect for the club."
Tanganga is a big plus for Tottenham right now and Mourinho's faith in him is a positive.
Spurs are away at Southampton in the FA Cup later this month, the stadium where they lost 1-0 on New Year's Day.
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