The 5ft 9in centre-back has received a mixed reaction from pundits since arriving at the club.
But Old Trafford great Stam, who comes in at a lofty 6ft 3in, has asserted that tall players can also be caught out due to their stature with the tactics of Erik ten Hag the most important thing for Martinez.
“That was an easy one, the day when he signed for United, I had already said they will talk about his height," Stam told the MEN.
“Over here [in England], everyone thinks as a centre-back you need to be big and tall, otherwise you won’t make it.
“The thing is, you need to look at the big picture of how the manager wants to play because that’s the most important thing. He wants to play dominating football, meaning you need to have players at the back who are comfortable on the ball.
”Of course, sometimes he’s going to get surprised, but that’s what also happens with big players - they make mistakes as well.
“Martinez shows his quality on the ball, he shows his quality when defending and his communication around him is good. He just needs to keep going.”