Ange Postecoglou admits poor first half cost Tottenham at Galatasaray
Spurs went to Istanbul on the back of three wins from three in the competition, but by half-time they were 3-1 down and ended up losing 3-2.
"Obviously, disappointing result. First half wasn't great, we just didn't handle things well at all," Postecoglou told reporters.
"Particularly with the ball, just really wasteful and gave it away way too many times, unnecessarily. That allows them to get a foothold in the areas that they're good at.
"I think that first half ultimately cost us the game and disappointing for us."
Spurs were punished for sloppy defending against a side which boasts the attacking talents of Mauro Icardi, Dries Mertens and Victor Osimhen, who netted twice.
"They got some good players in the front third and we just allowed that to happen way too often and ultimately paid a price for it," Postecoglou said.
"Because I thought, you know we always finish strongly and I knew we would in the second half."
That second half got even tougher when Spurs went down to 10 men after the sending-off of Will Lankshear, who had earlier scored his first goal for the club, but they did manage to pull a goal back through Dominic Solanke.
"Obviously, going down to 10 men didn't help, but even with 10 men, I thought we probably played the best football we did all game and got our second goal," the manager said.