The January signing has barely featured for the Toffees since signing from Lokomotiv Moscow, with fans becoming concerned by his absence.
However, the 26-year-old was handed the opportunity to start for Everton against Bournemouth in their most recent fixture.
And Martinez said: “We brought Oumar Niasse in, he was voted the best Footballer in the Russian League.
“He is a player who can be very important for us. When he arrived in January it was a moment in which he needed to work on his fitness.
“Finally now we’ve been able to put him on a level in which he’s been able to compete.
“He’s not the finished article because he’ll need a bit of an adaptation period but I thought his contribution was important.”
Niasse has made just four appearances for Everton in the Premier League since arriving, with his showing against Bournemouth being his first opportunity to start.
The Senegalese front man has failed to score in an Everton shirt to date, and his future still does not seem entirely certain.
A report in the Daily Mail last week, suggested that a senior member of Everton’s backroom staff had been totally unconvinced by Niasse’s performances in training.
Niasse is running out of time to impress this season, with Everton having just three games remaining.
The Toffees take on Leicester City, Sunderland and Norwich City before the end of the campaign.