Nathan's loss will be felt in the ninth inning, but odds are that someone from within the organization (or outside of the organization) will be able to step into that closer role without costing the team too many wins. Yet, beyond just losing a closer, the Twins are losing 70 innings of excellent, high-leverage performance in Nathan. While the current bullpen members will have to step up and fill that void, that still leaves 70 innings that will have to be filled by a player who might not have even been on the roster otherwise. As such, the Twins' bullpen depth will be tested this year in Nathan's absence.
Fortunately, if ever there was an acceptable time for the Twins to lose their elite closer, this is it.
The aforementioned return of Neshek, combined with the return of every key member from last year's relief corps and the presence of a few seemingly ready and capable arms in the high minors, gives the Twins more bullpen flexibility than they've had in past years. Nathan will be missed, but there are enough quality arms here that the Twins should be able to withstand his loss.
Let's take a look at the five pitchers likely to make the bullpen out of spring training, as well as a few others who have a shot at the sixth and (maybe) seventh spots or could get a shot to step in at some point during the year.
2009 Stats: 76.1 IP, 2.36 ERA, 47 K / 16 BB, 0.97 WHIP
Guerrier was spectacular last year, ranking among the league leaders in appearances for a third straight season while allowing less than one baserunner per inning and holding opponents to a .207 batting average. It was the second time in three years that Guerrier has been one of the league's best setup men, and I suspect that his proven ability in that role will deter Ron Gardenhire from trying to nudge him into the closer spot despite the numbers suggesting that such a course of action might make sense. Be wary, though; Guerrier's tremendous overall numbers last year were buoyed by an unsustainable .214 batting average on balls in play, and there's no telling whether the extensive wear on his arm over the past few seasons might start to creep up on him again like it did late in the 2008 campaign.
2009 Stats: 51.2 IP, 4.70 ERA, 43 K / 27 BB, 1.45 WHIP
2009 Stats: 61.2 IP, 2.34 ERA, 55 K / 23 BB, 1.18 WHIP
Over his first 81 major-league appearances, Mijares has posted a 2.12 ERA while allowing only 53 hits in 72 innings. Those are outstanding numbers, and they're largely the result of proper usage; he's held left-handed hitters to a minuscule .458 OPS and Gardenhire has given him the opportunity to face a lot of lefties. If his role is expanded too much, Mijares' mediocre control and susceptibility to righty hitters are likely to become liabilities. Fortunately, Gardy seems to recognize those flaws, which is why Mijares isn't being viewed as a legitimate contender for the closer role and why he'll likely keep the same LOOGY label this season.
2009 Stats: 42 IP, 3.00 ERA, 25 K / 14 BB, 1.21 WHIP
The Twins nabbed Condrey after he was non-tendered by the Phillies this offseason, and will pay him $900K to handle middle-inning duty in the bullpen. That's a higher sum than they'd have been likely to pay either Bonser or Bobby Keppel, who were both sent packing, so clearly the Twins have faith that Condrey can be a valuable piece. The veteran righty has posted a 3.16 ERA in 111 innings over the past two seasons. He doesn't strike many people out but has registered exceptional ground ball rates in each of the past two years, so his four homers allowed this spring shouldn't be too alarming.
Coming into the spring, Neshek seemed like a lock to open the season in the minors. In spite of his successful big-league track record, he hadn't pitched in a big-league game since May of 2008. However, Neshek has looked great this spring, and with Nathan gone the Twins will be needing an extra right-handed power arm for the late innings. Quickly, Neshek's chances to coming north with the team seem to be improving, as do his chances of ultimately taking over ninth-inning duties.
I mentioned Duensing as a candidate to start the other day, but if he makes the team out of spring training my guess is that it will be as a long reliever. He'd give Gardenhire an extra left-handed option behind Mijares, and his history as a starter makes him a good candidate to pitch in long relief.
Mahay spent the final month or so of the 2009 season with the Twins and performed well as a second lefty specialist. Just this week, the team re-signed him to a minor-league contract. He's 38 years old and no one's idea of a dominator at this point in his career, but it wouldn't come as any surprise to see him round out Gardenhire's bullpen.
Drafted out of college as a 22-year-old and moved somewhat methodically through the Twins' system, Slama isn't viewed by many as a great prospect because of his advanced age. However, it's tough to look past his absolutely spectacular minor-league numbers, and he's been outstanding in limited duty this spring. I doubt he'll make the team out of spring training, but I'd be stunned if he's not pitching for the Twins by July.
Delaney has risen through the minor-league ranks alongside Slama and posted similarly strong numbers. He needs to prove himself over a prolonged period at Triple-A, but he's another guy who can be called upon at any point this season and figures to be a productive big-league reliever.
A converted starter, Burnett had tremendous success last year in his first season as a full-time reliever, posting a 1.85 ERA and 0.97 WHIP in 78 innings split between Single-A and Double-A. He'll presumably open this season in Rochester, where a strong showing could get him a big-league look. Unlike Slama and Delaney, though, Burnett is still quite young (only 22) so he won't be rushed.