Belgium were without key players Kevin De Bruyne, Axel Witsel, Eden Hazard and Thibaut Courtois ahead of their Euros opener on June 12 against Russia.
Thorgan Hazard had opened the scoring in the first half but Greece levelled in the 66th minute from Georgios Tzavellas.
Martinez said: “We needed a game like this. You don’t learn anything that you win 3 or 4-0.
“I wanted a competitive team like the ones we are going to face at the Euros. That’s why we chose Greece. We knew it would not be a friendly match against them.
“I am not disappointed because this game was not scheduled to be won. It was played so that all the players could level up.
“Many players have accumulated the playing time necessary for the Euros.”
Elsewhere on Thursday, Switzerland tuned up with a comprehensive 7-0 victory over minnows Liechtenstein with Mario Gavranovic netting a hat-trick.
Ukraine defeated Northern Ireland 1-0, while Turkey got past Moldova 2-0 and the Republic of Ireland won 3-1 away to Andorra.
Ukraine are in Group C for the Euros along with the Netherlands, Austria and North Macedonia, while Turkey is pooled with Italy, Wales and Switzerland in Group A.