The Republic of Ireland winger signed for Everton during the January transfer window after spending two months languishing on the sidelines following a disagreement with former club Spartak Moscow.
Because of this, the 27-year-old was playing catch-up in fitness terms for his first few weeks at Goodison, but is now closing in on a first team start.
And speaking to the Liverpool Echo, Martinez was full of praise for the former Celtic man.
He said: "He has been putting in extra work, working really hard. It's about him setting certain levels to make sure he's fully fit soon.
"I think when he is he'll take us to a different level in terms of our forward play.
"With Aiden we had to start from scratch in terms of building up the fitness levels that he needed and we can already see he's a phenomenal player.
"He has great technical ability and it's important to get him feeling sharp so he can show that.
"He's settled in really well and over the next few weeks I think we'll see him ready to really help our season."
McGeady will hope to feature in Saturday's home clash with West Ham United in the Premier League.