Alcaraz, 31, has made just three starts for the Merseyside club this league season, and will be paired with John Stones at the back for the first time since January when they visit St Mary's.
The Paraguay international will step up in the absence of Sylvain Distin and Phil Jagielka, and Martinez had no doubt he would help Everton in their race for a UEFA Champions League spot.
"I think Antolin's biggest strength is his mentality," Martinez told the Liverpool Echo.
"I've seen him many times playing for Paraguay in the worst possible circumstances against the best strikers in world football and he's been able to cope with that with ease.
"He has incredible composure on the ball. I've seen him face Brazilians in the Copa Libertadores. I've seen him score against Italy in the 2010 World Cup which got his country a 1-1 draw.
"He reads the game well, understands the play and he's outstanding in the air. Then he's good in one versus one scenarios so as a defender he has a real advantage on strikers because of those attributes.
"He can come out on top of strikers every time."
Alcaraz was chided for his performance in their 4-0 derby loss to Liverpool, his most recent league appearance.
But Martinez said the former Wigan and Club Brugge man had excuses for his performance.
"Like any player it's important he's 100 per cent on the pitch, and in the derby he wasn't 100 per cent he just put himself forward because of the problems we had at the back," he said.
"That day both our centre-backs weren't really fit but they wanted to help the team and be available.
"Since then we've been able to give him a lot of volume of work and so to have him, with all his experience, for the final three games is a big plus."
Goalkeeper Tim Howard said he trusted the new-look partnership of Alcaraz and Stones, despite their lack of experience together.
"I don't think anyone can deny how well he has played. He has fitted right in like a glove. He is a natural," Howard said of Stones.
"And, of course, with Antolin, his experience speaks volumes. He comes right into a big match, reads the game really well and is so confident and composed on the ball."
