MESA, ARIZ. ? Manager Lou Piniella made it official Tuesday: Wade Miller will be the Chicago Cubs’ fifth starter. It means one-time 18-game winner Mark Prior could start the season in the minor leagues.

“He’s going be our fifth starter, OK?” Piniella said of Miller. “He’s pitched well in camp. He’s earned a spot.”

Miller, who had shoulder surgery after the 2005 season with the Red Sox, appeared in five games with the Cubs last season. But this spring he’s 2-0 with a 3.63 earned-run average in five starts. The right-hander was 16-8 and 15-4 in 2001 and 2002 with the Astros.

Prior, meanwhile, has made just three appearances this spring and is 0-2 with a 9.82 ERA, although he pitched well last week, allowing one a run in four innings.

With Kerry Wood nursing a sore shoulder and likely to start the season on the disabled list, it means the Cubs will open up without the two pitchers who led them to within five outs of the World Series in 2003.

“Remember our posture here with both Prior and Wood has been the same. It hasn’t changed since we got here,” Piniella said.

“Whenever they are ready, they’re ready. I’ve seen some nice improvements from Mark. He’s worked hard. The other kid (Miller) pitched well. In fairness, what do you do?”

Prior is scheduled to pitch today, and Piniella said a decision on his future could be made after the start.

“I don’t know. We’ll figure that out in the next couple of days. I don’t know,” Piniella said. “Obviously he needs to continue pitching. But I don’t have an answer.”

Prior began the last three seasons on the disabled list with Achilles, elbow and shoulder problems respectively. He was limited to nine starts a year ago with a sore shoulder.

Wood, who had a partially torn rotator cuff that he rehabbed during the offseason, has shown some improvement since he hurt his shoulder during an inning of relief Sunday.

Piniella said there was a possibility that Wood could throw on flat ground when he was able to tolerate it. Wood is taking medication for the shoulder, Piniella said.

“Actually the news is a little bit encouraging,” Piniella said. “He feels better and that’s the important thing. We’ll go from there.”

Piniella said the Cubs would lean toward carrying 12 pitchers instead of an extra outfielder, meaning Angel Guzman will be in the bullpen.

The Cubs have four outfielders in Alfonso Soriano, Matt Murton, Jacque Jones and Cliff Floyd. Chicago has depth there because infielders Mark DeRosa and Ryan Theriot also can switch and play the outfield. That means outfielder Angel Pagan probably will not make the opening-day roster.