Tom Selleck -- Tell Shaq I Would Dominate Him ... In a Free Throw Contest

It's "The 'Stache" vs. "The Diesel" ... Magnum P.I. vs. Kazaam ... old guy vs. older guy ... 'cause Tom Selleck is calling out Shaq ... telling TMZ Sports he'd crush the big fella in a free throw contest.

Tom was at LAX when our camera guy asked the former USC basketball player who would win if he took on Shaq Daddy in a battle from the charity stripe.

Check out the vid -- when he realizes we're just talking about a free throw shooting competition, Tom TOTALLY calls out O'Neal, not only saying he'd win ... but telling us to tell Shaq he's calling him out.

For the record -- Tom scored only 4 total points for USC, but Shaq missed over 5,000 free throws during his NBA career, so I guess we're saying ...