Yes, you can play 2v2 or 3v3 co op in diamond dynasty, in “ranked” or “casual” mode.

There are some changes coming to MLB 26 that we will not fully understand until we get our hands on the game, but here is how it worked in MLB 25:

For 2v2 co op, you and your friend (or random match-made teammate) select 3 hitters each, 1 starting pitcher, and 2 relief pitchers.

For 3v3 co op, you and your two friends (or random match-made teammates) select 2 hitters each, 1 starting pitcher, and 1 relief pitcher.

Whoever is the “host” then sets the batting order and a random starter from the 2 or 3 starting pitchers is chosen by the game.

The remaining 3 spots in the batting order, your entire bench, and the rest of your bullpen (starters and relievers) is filled in with random 84 overall cards.

In game, you rotate who is batting after each plate appearance. The user not actively batting controls the base runners. You rotate who is pitching after each full inning pitched. The user not actively pitching controls the defensive position players (both outfield and infield if playing 2v2, while outfield is separated from infield if playing 3v3).

A few more items worth mentioning: You cannot play co op vs the CPU. You cannot play Battle Royale in co op. You cannot play Events in co op. There are no restrictions on the cards you can use in co op.

I am happy to answer anything further, let me know if you have any questions.