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.