'I'm always [honest] I thought he wouldn't play.
Wenger had claimed Lacazette suffered a groin injury during their 5-0 win over Huddersfield and would not be available for the United game. "We weren't sure he would play but he tried and he played, that's part of football".
The Arsenal boss insisted he is always honest and maintained that he thought the France global striker would not be fit to start.
"I am very angry because the team produced a quality performance with desire, they were strong mentally and overall in a game of that stature to have 33 shots on goal and nothing to show for it..."
"He had tests on Friday morning and we thought he wouldn't play".
"If I am a player, and I think with what we produced, we have a huge potential, and we lose the game, we can not accept that".
When asked about Mourinho's comments, Wenger said: "I thought he wouldn't play but in the end he could play".
"That's why it's important in these rounds that we give some young players experience". Indeed, only defender Shkodran Mustafi has been ruled out having picked up a minor thigh injury at the weekend. The Gunners return to Premier League action away to Southampton on Sunday.
The Manchester United and Arsenal bosses have a fractured relationship after their numerous fall-outs over the years.
"It's not ideal", he added. It depends as well on what you do.
"You can do ice skating by bringing your child on and just making sure nothing happens to him, or (you can do) ice skating violently, I don't think he did that".
Following Wenger's press conference, the club announced on Wednesday that youngsters Eddie Nketiah, Ben Sheaf and Matt Macey had penned new deals.