The Twins entered 2009 with high hopes, and among the reasons for optimism was the starting rotation.

Scott Baker. Francisco Liriano. Kevin Slowey. Nick Blackburn. Glen Perkins. The five finished the 2008 season with a combined 52-34 record and a 4.08 ERA (inflated by Liriano’s early-season struggles), and none was even 28 years old. The Twins used just seven starters all that season.

That young rotation collapsed this year. All but Blackburn spent time on the disabled list. All showed signs of regression when they did pitch. Combined record for the five: 41-41, 4.91. And the Twins have used 11 starters.

What to expect in 2010?

Baker, Slowey and Blackburn figure to be in next season’s rotation.

Baker opened ‘09 on the DL and had a rough beginning when he returned, but he’s clearly their most reliable starter. Slowey was 10-1 before the wrist injury wrecked his season. And while Blackburn has had a miserable second half, he is the only guy to make every start the past two years.

Baker and Slowey can be top-three starters on a quality team. Blackburn strikes me as comparable to Carlos Silva or Bob Tewksbury: If he’s your fourth- or fifth-best starter, you’ll play in October; if he’s your best starter, you’re finishing last.

That leaves two-plus slots to fill (two-plus because it’s a rare team that needs just five starters over the course of a season. Depth is a necessity).

Ideally one will be capable of challenging Baker and Slowey for the role as lead dog. Realistically, the in-house candidates are more apt to challenge Blackburn. Also realistically, the Twins are unlikely to import a high-ceiling starter.

The candidates:

Brian Duensing: It would be difficult to be more impressive so far. He has a 2.00 ERA as a starter, albeit in just 36 innings over six starts.

But there’s little in his minor league record to suggest that’s an accurate measure of his ability, and judging from the quick hook on Tuesday, Ron Gardenhire isn’t sold on him yet.

Liriano: The memories of 2006 die hard, but this was a lost season for Liriano. He’ll be in the bullpen the rest of the way, and will get limited work.

He represents a major talent assessment problem. Is he capable of being a star starter, or should he be in the bullpen?

My guess is he should be a reliever, but that the Twins have too much invested in him emotionally to give up on him as a starter.

Carl Pavano: The free agent-to-be has had a 3.65 ERA since joining the Twins in early August with five quality starts in seven tries. He certainly fits the Twins strike-throwing mold.

On the other hand, he’ll be 34 next year, he’s thrown more innings this season than in the previous three combined, and his injury history is extensive. The chances that he’ll approach 30 starts/200 innings in 2010 are remote.

Perkins: The lousy pitching and recurrent injury questions were grating enough. The notion of filing a grievance over arbitration eligibility suggests he’s out of touch with reality.

He’ll be in the minors or in another organization next season.

Anthony Swarzak and Jeff Manship: Uh, no. More seasoning is required in both cases.

Boof Bonser: He’ll have to show first that he’s healthy, second that he can work deeper into games than he did in 2007 and 2008. I think his future is in the bullpen.

What they’ll do: They will re-sign Pavano (or bring in someone similar) and give Liriano one more shot as a starter. Duensing will be Plan B, the guy who gets the call when someone else flops or gets hurt.