Arsene Wenger called referee Michael Jones' decision to award Stoke’s match-winning penalty "a nice gift" as the Gunners suffered “a massive setback” in losing 1-0, and in the process fell four points behind Premier League leaders Chelsea.
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Jon Walters struck from the spot at the Britannia on Saturday after Laurent Koscielny had been adjudged to have handled the ball in the box late in the second half.
"It was a nice gift from the referee," Wenger said. "Koscielny is one yard away. He has no time. How can he take his hand away? He has no chance.
"It was a generous penalty. I can show you 10 videos of that situation when a penalty isn't given."
Wenger also admitted the defeat was a "massive setback" in Arsenal's title bid, with Chelsea taking full advantage of the slip up with a 3-1 win at Fulham.
"To win a title -- when you're expected to perform, you have to perform. It's as simple as that," Wenger continued.
"It is not a slight worry, it is a massive setback. We didn't create enough and they defended very well. Our performance today wasn't good enough.
"We are unlucky to lose this game, but our offensive game was poor."
Wenger also defended his decision to leave Mesut Ozil on the bench until the 66th minute, when he replaced Lukas Podolski.
Ozil was left out of the squad for Arsenal's home win over Sunderland last weekend, following his crucial penalty miss in the 2-0 Champions League defeat to Bayern Munich amid criticism of his recent performances.
"He [Ozil] was fit to start," said Wenger. "He has played many, many games, and he came on at the right moment I think."