KANSAS CITY, MO. - Righthander Esmerling Vasquez, who never has thrown a pitch for the Twins, is expected to be called up from Class AAA Rochester on Saturday and start Sunday against the Royals.

Righthander P.J. Walters -- remember him? -- is close to returning and might rejoin the starting rotation.

Lefthander Scott Diamond, who is serving a six-game suspension for throwing at Josh Hamilton's head, will return to the rotation next week.

So, is that a six-man rotation?

"Or seven or eight," Twins manager Ron Gardenhire said. "We're just going to get through the year."

Gardenhire and General Manager Terry Ryan talked about the state of their starters as rain -- part of what used to be Hurricane Issac -- poured on Kauffman Stadium. Friday's game was postponed and scheduled to be made up as part of a doubleheader to begin at 3:10 p.m. Saturday.

Welcome to September baseball, where contenders watch the scoreboard and noncontenders watch tryouts for next season.

For the Twins, that means they will address the one issue that has held them down all season -- the starting rotation. They are expected to look outside of the organization during the offseason for starting pitching, but they continue to evaluate what they have in-house.

Vasquez, claimed off waivers last September from Arizona, is 9-6 with a 2.78 ERA in 31 games, including eight starts, for Rochester. Vasquez, 28, has been starting recently and is expected to take the ball Sunday.

Walters was called up in May and made seven starts for the Twins, some of them impressive, before landing on the disabled list because of shoulder problems.

Vasquez has a good fastball. Walters, 27, has an average fastball but can set up hitters. Both will try to impress an organization that desperately needs starting pitching. Twins starters have the highest ERA in the American League (5.46), and only Colorado is higher in all of baseball.

So who is going to step up? The Twins have seen flashes from all their inexperienced pitchers. Such as righthander Samuel Deduno.

Deduno shut out Seattle on two hits over seven innings Wednesday, his finest outing since being called up in early July. He has a live fastball, so live that he's not sure how it will move once it leaves his hand. But he's throwing extra bullpen sessions between starts and working with pitching coach Rick Anderson to fine-tune his control. He is 5-2 with a 3.72 ERA, so something is falling into place. And he has put himself in the picture for 2013.

"I would say that he's put himself in the mix," Twins General Manager Terry Ryan said. "After what you saw the other day, that's a no-brainer."

Diamond (10-6) definitely has pitched himself into the rotation. And former Gopher Cole De Vries has, at times, shown a knack for getting hitters to chase pitches out of the strike zone. Can he improve his candidacy? Righthander Liam Hendriks is 0-7 with a 6.02 ERA but put it all together in a tough 1-0 loss to Seattle on Monday. Has he turned the corner?

Rosters are expanded on Sept. 1 each year to include players on the 40-man roster. The Twins have 37 spots filled, but Vasquez and Walters would take two more of them. They are expected to call up more players next week. Is Class AA New Britain outfielder Aaron Hicks in the mix to be added to the roster? Will Rochester reliever Anthony Slama, with a 1.13 ERA for the Red Wings, finally get another chance to prove he can get major league hitters out?

We'll find out in the coming days. But the one constant this month will be the attention given to the starting pitchers.

"You just want to see improvement," Gardenhire said. "Like Hendriks the other night; he kind of figured it out a little bit. Hopefully he can maintain it. He'll get more experience, and he'll be able to maintain everything in the process of developing at the major league level.

"Same thing with Cole De Vries; we'll see how the rest of the year goes. And Scott Diamond. We're seeing a pitcher in the making, and doing very well with it. Now it's about finishing out the season and giving us chances to win. That gives us tougher decisions to make next spring when we start looking at a pitching staff. That's what you hope those guys do, make it tougher."