Since his return he has consistently unlocked defences with a series of skilful displays, scoring thrice for Everton in all competitions and laying on six assists in the Premier League.
"It's his maturity that impresses me," Martinez was quoted as saying by the British media after the game. "Two years ago when we had him first we knew he was a young man with an incredible natural talent but now although he's young in age he's very mature.
"He has a big role for us and he's been very consistent which is difficult for a wide player. That's what impressed me the most.
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"When Geri expresses himself the end product comes with it. When you play in the street as a kid that's what you do; you try to take people on, you have a shot.
"He enjoys what he does and has a desire to score, but his work-rate impresses me too."
The manager also praised his team for bouncing back with a clean sheet against Boro after twice letting a lead slip to draw 3-3 with Bournemouth in the Premier League at the weekend.
"The two goals were exceptional pieces of quality which you can never take for granted," Martinez said.
"But, after going 2-0 up, to keep the clean sheet was probably the most pleasing aspect.
"We knew whoever you play away from home you need to be mature and control the game and I thought we did that really well, especially after what happened after the weekend when we went 2-0 up."
(Reporting by Simon Jennings in Bengaluru; editing by Sudipto Ganguly)
