PEORIA, Ariz. -- The Brewers made their first serious round of roster cuts on Friday, and there were few surprises. Manager Ned Yost knows the tough ones are yet to come.

Infielder Hernan Iribarren, left-hander Zach Jackson, first baseman Brad Nelson and right-hander Luis Pena, all of whom were expected to begin the year at Triple-A Nashville, were formally optioned there. The quartet will cross the parking lot at Maryvale Baseball Park just in time for the first game of the Minor League spring schedule, against Oakland's top affiliate on Saturday.

Yost's most dreaded cuts will come later and will affect the starting rotation. The Brewers have a slew of capable arms -- Dave Bush, Chris Capuano, Manny Parra, Claudio Vargas and Carlos Villanueva -- competing for three open spots behind Ben Sheets and Jeff Suppan to start the season.

"I'm going to have two guys go to the Minor Leagues who are big league pitchers," Yost said. "I don't know who they are going to be. For me, Parra, Villanueva, Vargas, Bush, Capuano are big leaguers.

"I don't have any sense who it is yet. But that's the way that it's probably going to be. I'm trying to figure out the best way for our organization and our team. That's what happens when you get into a championship situation."

Bush, Capuano, Parra and Villanueva all have Minor League options remaining. Yost has spoken often this spring of maintaining organizational depth, meaning someone who would have made the Opening Day roster, say, four years ago, now will have to go to the Minors to lay in waiting.

"I detest it," Yost said. "I'm taking notes. I'm already dreading it.

"When you send guys down, you'd better have a detailed plan of attack," Yost said. "A detailed plan to get them back. I've been breaking down each pitcher, their strengths, their weaknesses. What do they need to get better at? What are their pluses? What are their minuses?"

Vargas added to his pluses on Friday, when he worked five strong innings and limited the Padres to three hits including Chase Headley's solo home run and exited with a 3-1 lead. In four appearances this spring, Vargas is 3-0 with a 2.40 ERA.

"I think I have a good chance to start, to stay in the starting rotation," said Vargas, whose lead grew to 4-1 in the sixth when Prince Fielder hit his first spring homer. "But we'll see. I want to keep working and doing the same thing."

Yost said Vargas "stepped up again." Is that possible when it's what he has done all spring?

"He's holding his own," Yost said. "I don't know if it's 'stepping up,' but he's done real, real nice. He's commanding three pitches."

For the four players cut on Friday, the work will continue in Minor League camp. Either Yost, general manager Doug Melvin or assistant GM Gord Ash chatted individually with Iribarren, Jackson, Nelson and Pena to discuss the road ahead.

Pena was extremely impressive in Spring Training, working a scoreless inning in each of his six appearances, and he could emerge as Nashville's closer. Jackson was 0-1 with a 3.38 ERA in three Cactus League games and will be in Nashville's starting rotation. Iribarren hit .300 in spring games and has batted .324 in six Minor League seasons mostly as a second baseman, but now he will get an extended look in center field. Nelson batted just .154 in 10 spring games and will play first base, third base and outfield for the Sounds.

Yost does not take cuts, even these in the early going, lightly.

"You'd better not just tell somebody, 'You're going down to go down,'" Yost said. "It's, 'This is why you're going down. This is what you need to do to get back.' You'd better have your ducks in a row, and you'd better have answers for them."