The Spaniard has questioned the amount of contact Gareth Barry made on Alex Oxlade-Chamberlain following Everton's FA Cup exit at the quarter-final stage
With the quarter-final delicately poised at 1-1 after Romelu Lukaku had cancelled out Mesut Ozil's opener, Gareth Barry was penalised for tripping Alex Oxlade-Chamberlain inside the penalty area.
Former Everton midfielder Mikel Arteta put Arsenal back in front from the spot, then Olivier Giroud struck twice as Arsene Wenger's men boosted their hopes of ending their nine-year trophy drought with a 4-1 victory at the Emirates Stadium.
"I still feel the penalty is a very soft call," Martinez told ITV.
"It's the key moment and I felt obviously it's a situation where Gareth is fighting with him for the ball. There is contact but is there enough contact for a penalty?
"The second goal was going to change the game completely. That second goal was vital, we wanted to make sure we had the opportunity to score that."