Andre Villas-Boas denied complacency got the better of his Tottenham team after they threw away a lead to leave Panathinaikos with just a point.
Spurs were in complete control of their Group J game against the Greek side and took the lead after 35 minutes when Michael Dawson glanced Tom Huddlestone's cross past Orestis Karnezis.
Jermain Defoe, Gareth Bale, Clint Dempsey and Huddlestone then all missed chances to put the game to bed and Panathinaikos took full advantage through striker Toche, who left Dawson for dead and converted Giorgos Seitaridis' through-ball 13 minutes from time. But Villas-Boas insisted: "I don't think we were complacent."
Panathinaikos, who sit 12th in the Greek Super League after a dismal start to their season, lacked any penetration until the latter stages of the second half and were there for the taking.
Villas-Boas, whose team now sit third in Group J, two points behind Lazio, brushed aside suggestions his team thought the game was over before the final whistle.
Villas-Boas added: "We have to give credit to Panathinaikos, they pressed much more and started to gain belief from that and that led to the goal. I think the whole team felt a bit disappointed because the first half was so positive and we were in control of the situation.
"We were a bit sloppy in the second half. I understand the disappointment at not putting the game to bed, but in the end we congratulated the players because if it had been other way round, the whole perspective would have been different.
"Panathinaikos came at us very strong in the second half, they made a change with Ibrahim Sissoko. He improved the quality of their game and (we) could not stay in control of game so much in second half."
With Lazio beating Maribor in the other game, Spurs may find it hard to qualify if they fail to beat the Slovenians in their next game, but Villas-Boas is not panicking.
"In the end it leaves us with two points. Maribor have three and Lazio have four so everything is open as we go into the double-headers," he said. "It's only after the fourth game that you tend to know who will go through or whether there is any competition for that second place. In a group like this, normally 10 or 11 points to qualify."