AaronGleeman.com

Pat Neshek has been diagnosed with a partially torn ulnar collateral ligament is his right elbow, which while not quite the worst-case scenario is bad enough that he's likely done for at least the remainder of this season. Neshek will completely eschew throwing for three months and general manager Bill Smith indicated that the goal is to have him ready for spring training, but a partially torn UCL is just one small step away from Tommy John surgery and the 12-18 month recovery that follows.

Like many pitchers with non-traditional deliveries Neshek has always had plenty of skeptics, including the Twins. He didn't make his MLB debut until two months before his 26th birthday despite a 2.18 ERA in five minor-league seasons, but Sideshow Pat quickly established himself as an elite setup man after being called up from Triple-A in July of 2006, posting a 2.19 ERA, 53-to-6 strikeout-to-walk ratio, and .176 opponent's batting average over 37 innings.

Some skeptics still questioned the sidearming right-hander's effectiveness against left-handed hitters, so Neshek held lefties to .181/.288/.330 last year on the way to a 2.94 ERA, 74-to-27 strikeout-to-walk ratio, and .183 opponent's batting average in 70.1 innings overall. He had two ugly outings early on this season, but then put together seven straight scoreless appearances and entered Thursday's game with a 4.26 ERA, 14-to-4 strikeout-to-walk ratio, and .234 opponent's batting average in 12.2 innings.

Coming in with the Twins down 4-2 and two outs in the seventh inning, Neshek wriggled out of the jam that Juan Rincon and Dennys Reyes had left behind. He remained in for the eighth inning, allowing a leadoff single to Jermaine Dye before getting Nick Swisher on a swinging strikeout. Unfortunately, the pitch that got Swisher to swing and miss also ended Neshek's season. Immediately after unleashing one of his trademark frisbee sliders, a look of disgust washed over Neshek's face.

He stepped off the mound in obvious discomfort and failed to put up a fight when the trainer came to check on him, exiting the game and telling the dugout that he'd felt a "pop" in his elbow. Sure enough, an MRI revealed a partially torn ligament, which essentially means that Neshek has a less complete version of the injury that sent Francisco Liriano under the knife. For now Neshek is expected to avoid surgery, but the Twins tend to say that initially even with injuries that eventually require it.

A native Minnesotan who's used his quirky delivery to dominate hitters and his personal website to interact with fans, Neshek is about as popular as a reliever can be without saving games. He's also about as valuable as any non-closer reliever in baseball, compiling a 2.91 ERA in 120.2 career innings while going 11-5 with a 142-to-37 strikeout-to-walk ratio and .188 opponent's batting average. Upon hearing the bad news, Ron Gardenhire put it best: "He's one of the good ones."

During Neshek's career, exactly half of his work has come in the eighth inning and 45 percent has come in what are defined as "close and late" situations. He pitched in games that had margins of three runs or fewer 70 percent of the time, but unlike closer Joe Nathan was often asked to come in from the bullpen mid-inning, with runners on base and the Twins in a jam. Neshek will no doubt be missed getting three outs in front of a Nathan save, but more than that he was the bullpen's fire extinguisher.

From working the eighth inning setting up Nathan for another save chance or working multiple frames while facing the heart of a batting order to wriggling out of jams that he didn't create or rescuing another reliever from an ugly outing, Neshek was the Twins' first choice. Between being called up from Triple-A to striking Swisher out Thursday, he pitched in 121 of the team's 274 games (44.1 percent) and threw 120.2 innings. For comparison, during that same span Nathan threw 118 innings in 114 appearances.

Replacing Neshek will require finding someone to work the eighth inning prior to Nathan slamming the door, but it will also mean trusting other relievers to work out of jams in key spots any time after the sixth inning whether the Twins are winning or losing. Neshek allowed just 21.9 percent of the runners he inherited to score and if you prorate his post-promotion performance as a rookie to a full season, he ranked third among the AL's non-closer relievers in Win Probability Added in both 2006 and 2007.

It remains to be seen exactly how the bullpen will shake out sans Neshek, but Rincon, Reyes, Matt Guerrier, and Jesse Crain will likely each move one rung up the ladder, adding responsibility. For instance, Reyes will likely be pushed into longer outings while facing more righties after being used sparingly and primarily against lefties so far. However, right-handers Guerrier, Rincon, and Crain will probably shoulder most of the load. Here's how those three compare to Neshek since 2006:

                   ERA      SO%      BB%     OAVG     IRS%
Pat Neshek        2.91     30.1      6.6     .188     21.9
Matt Guerrier     2.92     16.0      6.6     .250     37.1
Juan Rincon       3.92     19.6      7.8     .268     37.7
Jesse Crain       3.99     17.9      5.2     .269     30.4

Guerrier actually has an ERA that's only slightly worse than Neshek's since 2006, but his strikeout rate is 47 percent lower, his opponent's batting average is 33 percent higher, and he's allowed 69 percent more of his inherited runners to score. Guerrier has been a fantastic middle reliever over the past three seasons and at times has done a solid job in the eighth inning, but he'd be a definite step down from Neshek in front of Nathan.

Rincon figures to be even more exposed if handed eighth-inning duties, which is interesting given that it was his decline in 2006 that opened the door for Neshek to emerge as the team's top setup man. Rincon has declined even further since then and has mediocre numbers across the board over the past three years, but has looked somewhat improved early this season and will almost certainly be given a bigger role than a post-surgery Crain.

With Neshek the bullpen was the Twins' biggest strength and ranked among the best in baseball, so losing one reliever isn't going to wreck them. However, Neshek was clearly second only to Nathan in terms of importance to the bullpen and was probably a lot closer to Nathan than most people think. His injury pushes Guerrier, Rincon, Crain, and Reyes into expanded roles and the danger is that it may expose several of them by taking them out of comfort zones and stretching their ability.

Guerrier can do the job in the eighth inning if asked, but won't be as good as Neshek and moving him into the top setup job creates a hole in the sixth and seventh innings. Rincon, Crain, and Reyes can take on more responsibility and capably fill in those gaps, but they won't be as effective as Guerrier and putting more on their respective plates takes away some of the workload-related luxuries that fantastic depth previously provided.

Here's hoping that Neshek avoids surgery and makes a full recovery in time for next season, because he deserves it and the Twins need him.