Twins Insider: Diamond's struggle makes point about Twins' rotation

Lefthander Scott Diamond is back with the Twins and has a chance to boost his status for next year's rotation, but he forgot to pack one of his keys when he flew in from Class AAA Rochester — the key to unlocking the outer half of the plate.

Unable to hit his spots the way he needs to, Diamond was knocked out in the fifth inning Thursday in the Twins' 8-2 loss to Oakland. Diamond looked at the tape of his performance and realized that if he had thrown strikes on the inner half of the plate, especially to righthanded hitters, he would have set them up for pitches on the outside corner — or even off the plate.

The old saying goes, "pitch inside for show, pitch outside for dough." But Diamond nibbled at the insider corner and missed frequently. It was one of his problems when he was sent down after an outing on Aug. 1.

"I was missing three, four, five inches off, which is not effective for me," said Diamond, who is 5-11 with a 5.61 ERA in 21 starts. "I need to work closer to the plate. That would lead to more effectiveness and being able to put more hitters away."

The Athletics scored four runs in the third inning en route to winning the final two games of the three-game series at Target Field. The big blow was a two-run triple by Yoenis Cespedes on a ball that center fielder Alex Presley got turned around on.

Should Diamond be judged differently because of the misplay?

"It was still a rocket off the wall," Twins manager Ron Gardenhire said. "Let's not forget that ball was crushed."

The list of contenders for spots in the rotation is a long one — and could change considerably before the Twins face the White Sox on March 31 in the 2014 opener at U.S. Cellular Field.

Righthander Kevin Correia is the only starter under contract for 2014; he's scheduled to make $5.5 million next season. The Twins are getting their money's worth, as Correia is 9-11 and closing in on 180 innings.

Here are the rest of the pitchers who have started for the Twins this season: Diamond, Mike Pelfrey, Samuel Deduno, Kyle Gibson, Vance Worley, Pedro Hernandez, P.J. Walters, Andrew Albers and Liam Hendriks.

Walters could leave as a minor league free agent. Pelfrey will be a free agent and wants to return. The list doesn't include prospects Alex Meyer and Trevor May, who both should be in spring training camp with an outside chance to make the team. The other pitchers are under Twins control for next season.

That's enough for a six-man rotation for both the Twins and Class AAA Rochester. The problem is that list lacks front-line talent.

"If there's people out there better than what we have, then you have to consider them," Twins General Manager Terry Ryan said. "Sometimes you have turnover and sometimes you don't."

The Twins entered Thursday with a starters ERA of 5.06, the worst in baseball. That screams turnover, Terry.

A roster can improve with development, but it also improves by bringing in top-end talent and pushing everyone else down. There can't be another offseason of adding rotation stabilizers — the Twins already have plenty of those now in Diamond & Co.

It would be wrong to think that all of their answers to their pitching questions can be found in-house.

La Velle E. Neal III • lneal@startribune.com