MESA, Ariz. -- Guess who will be the Chicago Cubs' fourth starter? Sean Marshall.

"I always say I'm looking for a surprise," manager Dusty Baker said Thursday.

Marshall found out Thursday. The rangy left-hander will make his final spring start Friday night in Las Vegas against the San Diego Padres and then make his Major League debut on April 9 against the St. Louis Cardinals.

"I'm just going to take it like any other Minor League game I've pitched in my life and just do the same," said Marshall, who has not pitched higher than Double-A and has a career 14-13 record and 2.64 ERA in 44 Minor League starts. "There might be more people in the stands, but I'm up there for a reason."

The lefty hasn't given up a run in 10 1/3 innings over five spring games. Marshall, 23, never imagined he'd be in this position when pitchers and catchers reported to Fitch Park in mid-February.

"I've come a long way since the beginning of spring," Marshall said. "[Being put on] the 40-man was exciting enough. To be added to the 25-man roster and start for the Chicago Cubs is surreal."

He's already picked up on the impact Cubs fans can have.

"I had this home start [in Mesa] and it was awesome," Marshall said. "You strike somebody out and the place goes crazy. It just adds to the fuel."

Promoting Marshall means Jerome Williams will be the long man in the bullpen and in line to start April 15, the first time the Cubs need a fifth starter.

"You have to give him a chance to do better or a chance to not do well," Baker said. "Right now, [Williams] has to pitch.

"He handled [the news] well," Baker said. "It beats the alternative, too. It's a matter of him staying prepared and being prepared."

Williams, who gave up one run on three hits and four walks over five innings, hadn't heard anything.

"As long as I can help out the team any way I can, that's all that matters," Williams said.

Marshall's big-league debut will be in a nationally televised game. He expects plenty of family present. The Cardinals won 100 games last year and the National League Central Division.

"It's just a team," Marshall said. "It's a Double-A game to me. I'm not going to pitch any differently."

"I try to protect the young guys as best I can, but at the same time, if you're in the big leagues, you're in the fire every day no matter who you're playing," Baker said.

The Cubs will have two lefties in the starting rotation, and this will be the first time the team has used a southpaw in the opening series since 1997, when Terry Mulholland was the Opening Day starter.

Have a catch: Mark Prior, who will open the season on the DL for the third straight year, played catch on Thursday in his rehab from a strained muscle in his right shoulder.

"We're going to miss him big time but we know we're going to get him back, too," Baker said.

When will that be? June?

"I don't think it'll be that long," Baker said. "You hope not. He could come rather quickly, especially if he doesn't feel anything."

Roster moves: The Cubs optioned right-handed reliever Roberto Novoa to Triple-A Iowa. Novoa had been slowed this spring after suffering a respiratory infection. The Cubs decided he needs more time to build up his endurance.

The move left the Cubs with one final decision to make, but they have a few options. The Cubs could go with 12 pitchers on Opening Day, which means John Koronka would likely make the team, or they could decide to go with 11 and take infielder Ryan Theriot, or pick up a player who is placed on waivers by another team. Expect the final moves to be made this weekend in Las Vegas.

"The guys at the end are walking a tight rope until Opening Day starts," Baker said.

Second to none: Todd Walker, Jerry Hairston Jr., and Neifi Perez head into the final two games unsure about how much playing time they'll get at second base.

"It isn't much different than 'Walk' and [Mark] Grudzielanek," Baker said of the 2004 season. "They were both starters when they got here. It ended up we were lucky to have both of them when we got here."

That's because Grudzielanek was sidelined with injuries and Walker ended up playing 129 games for the Cubs.

"You'd rather have too many than too few," Baker said.

"If one guy does better than the other, obviously they get more playing time," Walker said Thursday. "That's how this system works. We all just sit back patiently and in the end, whether you play or not, you hope the team's winning. We're all pulling for everybody."

Walker has played good defense this spring.

"I'm happy I didn't give anybody a reason to say otherwise," Walker said. "I worked very hard at that. I actually hit the ball pretty well, too."

Baker has said having three second basemen is a good thing.

"I think he's right," Walker said. "Dusty's pretty smart. He'll put this thing together where the team we have, on any given day, has the best chance to win. I think we all believe that. Ronny [Cedeno] is not going to play 162 games, so Neifi will have to play some shortstop. Jerry and I will be the same at second base.

"When I came over here, I knew Dusty plays everybody," Walker said. "You need that. With a long season, you need guys healthy and rested. The more guys you have, the better you'll be."

It's been a strange spring for Walker, who has heard his name mentioned as possible trade bait because of the overload of infielders.

"It's not an ideal situation," Walker said, "but in the end, when you're looking at the team, the more quality players you have the better you'll be. It never goes the way you think it'll go. You start the season, and a week into it you have injuries. That's happened every year I've been in the big leagues.

"Regardless of the way it starts out, you have to have faith and confidence that you're going to be able to play eventually," Walker said. "Now's not the time to worry about yourself, it's time to focus on us as a team. If we can win, I think everybody can be happy."

Walker is a realist, too. He'd rather be playing full time. Anybody would.

"I think anybody who tells you they'd be happy sitting on the bench isn't telling you the truth," Walker said. "At the same time, Jerry's a good friend of mine. If he's playing, I'm going to support him. I hope he does well. We all hope the team wins. Same with Neifi. Neifi's a great, great person. Those are the type of people you get behind and support. I've relegated myself to whatever happens, I just want the Cubs to win and if that happens, I'll be happy."

Final tuneup: Reliever Michael Wuertz figured out what was wrong with his delivery. It was a minor mechanical thing. The change has fixed his confidence, too.

"When you're struggling, like I was at the beginning of camp, it's tough to make the adjustment," Wuertz said. "You're going out there and you're trying to battle so hard and you want everything to be perfect. You sometimes get out of your realm of things. When I tweaked my back a little, I realized I better make an adjustment.

"Larry [Rothschild, pitching coach] and Dusty both talked to me about making that adjustment and the last game I threw, it really carried over," he said. "I'm using my legs a little more and keeping my front shoulder in longer. It's just a little bit and it really seems to help. Everything just feels in sync now."

It was frustrating for Wuertz, who was coming off a solid season in which he led the Cubs in appearances with 75 games.

"I guess now is a good time to be throwing the ball better," he said. "Granted, you look at the stats and they don't look good, but it's more important the confidence I have back. That's the biggest thing is when you're struggling and your confidence is as long as it can get, you have to go out there and battle. When you get that confidence back, it makes you feel like a different person on the mound."

Quote of the day: "I like this team. I like this team a lot. I've heard we could be anything from a sub-.500 team to being [in the] World Series. I don't think anybody really knows. There are a lot of variables here, a lot of variables that could go really well." -- Baker, on the Cubs' chances

Extra bases: Aramis Ramirez belted a three-run homer in the first inning Thursday against Arizona's Orlando Hernandez to extend his hitting streak to 13 games. ... Kerry Wood will throw batting practice on Friday in Las Vegas, the first time the right-hander will face hitters this spring. Wood is rehabbing from arthroscopic shoulder surgery in late August, and making good progress. ... The Cubs drew a sellout crowd of 12,879 on Thursday, and finished the spring drawing 154,978 in 14 games at HoHoKam Park. ... The Cubs announced the newly renovated Wrigley Field bleachers will be officially named the Bud Light Bleachers.

Up next: Marshall will start Friday night in Las Vegas for the Cubs against the San Diego Padres at Cashman Field. The Padres will counter with Woody Williams. Greg Maddux is scheduled to start Saturday in his hometown in the Cubs' exhibition finale.