Manager Jim Riggleman is starting Rob Johnson at catcher and Luis Valbuena at second base today, and said he'll give Matt Tuiasosopo his first Major League start at third base on Friday.

"We're going to give these kids the opportunity to play a little," Riggleman said. "We want to look at them, and we want to let them get the butterflies out with that first game action.

"Then they can concentrate on just playing baseball."

The Mariners have already made heavy use of rookies like Wladimir Balenien, Jeff Clement Bryan LaHair, and given starts to pitchers Ryan Rowland-Smith, Ryan Feierabend and - on Friday - Brandon Morrow.

Now, the team gets to hold a month-long audition that also showcases young players they may want to trade in the off-season.