Emmanuel Adebayor scored the only goal of the contest in the 65th minute, showing brilliant skill and strength to fire low after a quickly-taken free-kick from Kyle Walker, but there could have been a chance of a late equaliser.
"I haven't seen the replay but it looked a very sloppy incident," Martinez said after the match.
"I think it was a careless challenge. He tries to win the ball and didn't at all.
"I'm not sure if there was enough contact for a penalty, but I've seen them given.
"You need a little bit of luck and it was one of those days for us."
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