Barkley has not started in the Premier League since February 1 after breaking his toe, but the Spaniard felt the midfielder showed signs he is getting back to his best at the Emirates Stadium.
"I thought he was a real threat, especially on the counterattack," Martinez told reporters.
"He had two or three incidents that, if we had been a little bit sharper, we could have taken advantage of.
"He looked powerful, fresh again after the injury. Overall, I thought his contribution was very good and back to his normal self."
The cup quarter-final defeat in London leaves Everton to concentrate solely on qualifying for Europe this season, and Martinez believes the lack of any distractions could help their cause.
"Of course, we're disappointed, but we have to focus on the 11 games we have," he added.
"It leaves ourselves with more focus in what we've got in front of us. It's probably easier now to focus on getting as many points as we can."