"He's still scheduled to be a starter, so we have to continue to try to stretch him out," Cubs manager Rick Renteria said Sunday of the Japanese lefty.
Another candidate, Chris Rusin, started Sunday, and James McDonald, a free agent who signed in February with the Cubs, will pitch on Monday in a split-squad game against the Athletics.
One name apparently not in the mix unless necessary is Carlos Villanueva, who will return to the role of swing man, a reliever capable of making a spot start or throwing multiple innings in a game.
"'Villa' was big for us last year with the [Matt] Garza situation," Cubs pitching coach Chris Bosio said in Mesa. Ariz., about Villanueva, who filled in when Garza was injured last year. "For me, Villanueva is probably one of the most valuable swing guys in all of baseball because he's done both and had an incredible start last year to the season."
Villanueva went 1-1 with a 2.29 ERA in five starts last April. He finished 1-7 with a 4.50 ERA in 15 starts and posted a 3.03 ERA in 32 relief appearances.
"He's been a swing guy here before, so I don't think we have any problem of him adjusting if he needs to," Renteria said. "He's capable of doing both."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. AJ Cassavell is a reporter for MLB.com. Follow him on Twitter @ajcassavell. This story was not subject to the approval of Major League Baseball or its clubs.