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Also in this series: 1-5, 6-10, 11-15, 16-20, 21-25, 26-30, 31-35.

40. A.J. Achter | Reliever | DOB: 8/88 | Throws: Right | Draft: 2010-46

YEAR     LV      G     GS      ERA        IP       H     HR      SO     BB
2012     A-     18      1     2.48      40.0      33      5      49     12
         A+     19      0     0.79      34.1      21      0      37      3
2013     AA     25      0     2.21      36.2      28      3      36     19
         AAA    16      0     3.04      23.2      17      4      20     14
2014     AAA    40      0     2.38      72.0      44      4      69     24

A.J. Achter was a 46th-round draft pick out of Michigan State in 2010 and posted a 4.52 ERA in 2011 as a starter at low Single-A, but he shifted to the bullpen in 2012 and has a combined 2.10 ERA in 213 innings as a reliever since then. That includes a 2.17 ERA and 80/25 K/BB ratio in 79 innings last season, mostly at Triple-A, which was enough to get him added to the 40-man roster as a September call-up.

However, his shiny ERAs come with good but not exceptional strikeout rates and Achter's control is mediocre. He's done an amazing job limiting hits, including a .173 opponents' batting average last season, but that was driven by an unsustainably great .228 batting average on balls in play. Toss in underwhelming velocity and his odds of sticking in the big leagues don't seem particularly good, but at age 26 he warrants a "why not?" look.

Achter got into seven games for the Twins as a reliever and posted another nice-looking 3.27 ERA, but he managed just five strikeouts in 11 innings, opponents hit .304/.347/.522 off him, and his average fastball clocked in at 90.2 miles per hour. Middle relief is Achter's upside and the Twins' bullpen depth chart is pretty crowded, but the fact that they kept him on the 40-man roster all offseason suggests they're interested in giving him another shot at some point.

39. Logan Darnell | Starter | DOB: 2/89 | Throws: Left | Draft: 2010-6

YEAR     LV      G     GS      ERA        IP       H     HR      SO     BB
2012     AA     28     28     5.08     156.0     193     22      98     47
2013     AA     15     15     2.61      96.2      96      4      77     23
        AAA     12     11     4.26      57.0      63      5      43     22
2014    AAA     23     19     3.60     115.0     108     16      90     49
        MLB      7      4     7.13      24.0      31      5      22      8

A solid 2013 season between Double-A and Triple-A got Logan Darnell added to the 40-man roster, but the 2010 sixth-round pick spent most of last year back at Triple-A and managed just 90 strikeouts in 115 innings while walking 3.8 batters per nine frames. That poor strikeout rate matches his high-80s fastball velocity and Darnell has an underwhelming 3.81 ERA and 133/71 K/BB ratio in 172 career innings at Triple-A.

He also got knocked around in his first taste of the majors, allowing 20 runs in 24 innings for the Twins at age 25. Given his sub par velocity, mediocre control, and inability to hold right-handed hitters in check it's hard to imagine Darnell having sustained success as a starter in the majors, but the left-hander could find a home in the bullpen as a southpaw specialist. Of course, that role is such that the same can be said for nearly every decent lefty in the minors.

In the minors during the past two seasons Darnell held lefties to a combined .228 batting average and 74/18 K/BB ratio, whereas righties batted .285 off him over that same span. Regardless of the role Darnell is behind a lot of names on the Twins' pitching depth chart heading into 2015 and seems like a candidate to be removed from the 40-man roster if space is needed early, but if given a chance he could carve out a useful niche in middle relief.

38. Levi Michael | Second Base | DOB: 2/91 | Bats: Switch | Draft: 2011-1

YEAR     LV      PA      AVG      OBP      SLG     HR    XBH     BB     SO
2012     A+     512     .246     .339     .311      2     20     56     82
2013     A+     375     .229     .331     .340      4     23     49     67
2014     A+     201     .305     .375     .395      1     12     19     25
         AA      63     .340     .444     .358      0      1      7     11

Levi Michael was billed as being close to MLB-ready when the Twins drafted the North Carolina shortstop in the first round in 2011 and the pick made sense for a team that had long struggled to develop capable middle infielders. They showed their faith in his readiness by sending him directly to high Single-A, but three years later Michael was still stuck there. Nagging injuries repeatedly derailed Michael's development and the solid power he showed in college disappeared.

Last season, in his third go-around at Fort Myers, he finally showed some promise by hitting .305 in 45 games to earn a promotion to Double-A, where he hit .340 in 15 games. Those lofty batting averages are misleading because he managed just one home run, but Michael controlled the strike zone well. Even within the overall struggles Michael always made plenty of contact and drew some walks, suggesting the switch-hitter could have value even if the power is gone for good.

Unfortunately he's no longer a shortstop. Dating back to college there were questions about his ability to stick at shortstop long term and last season Michael played almost exclusively second base at both levels. Not only does that raise the bar for his offensive production, it makes it much harder for Michael to potentially stick in the majors as a utility infielder. At age 24 and with just 15 career games above Single-A it's time for Michael to sink or swim.

37. Stephen Pryor | Reliever | DOB: 7/89 | Throws: Right | Trade: Mariners

YEAR     LV      G     GS      ERA        IP       H     HR      SO     BB
2012     AA     11      0     1.12      16.0       7      0      24      5
         AAA    16      0     0.00      20.0      11      0      20     11
         MLB    26      0     3.91      23.0      22      5      27     13
2013
2014     AAA    38      0     3.16      51.1      32      6      49     34

Acquired from the Mariners on July 24 as the Twins' return in the Kendrys Morales salary dump, Stephen Pryor was one of the few players on the 40-man roster not to get a September call-up to Minnesota. However, he remained on the 40-man roster all offseason and presumably the front office has enough patience in the 25-year-old right-hander to see if he can get healthy and regain his old velocity after missing most of 2013 and part of 2014 following shoulder surgery.

Before the injury Pryor looked destined for a late-inning bullpen role in Seattle. As a 22-year-old in 2012 he blitzed through the minors, going from Single-A to Double-A to Triple-A before debuting with the Mariners in June. Overall that season Pryor posted a 0.93 ERA and 47 strikeouts in 39 innings as a minor leaguer and then racked up 27 strikeouts in 23 innings for the Mariners while averaging 96.3 miles per hour with his fastball.

His arm gave out in 2013 and while Pryor returned last season to log 55 innings in the minors and make two appearances for the Mariners he was a shell of his former self, throwing in the low-90s with less than one strikeout per inning. Pryor has always struggled to consistently throw strikes and control problems that can be overlooked when attached to a high-90s fastball may be tough to overcome if that velocity is gone for good.

36. Lester Oliveros | Reliever | DOB: 5/88 | Throws: Right | Trade: Tigers

YEAR     LV      G     GS      ERA        IP       H     HR      SO     BB
2012     AA     13      0     1.42      19.0      10      0      16      7
         AAA    19      0     3.07      29.1      24      2      35      8
2013
2014     AA     26      0     0.89      30.1      17      0      36     14
         AAA    24      0     2.29      35.1      27      0      52     13

Lester Oliveros was acquired from the Tigers in the 2011 trade for Delmon Young and missed most of 2013 recovering from Tommy John elbow surgery. He returned last year and was better than ever between Double-A and Triple-A with a 1.64 ERA and 88 strikeouts in 66 innings while holding opponents to a .187 opponents' batting average with zero home runs. And then naturally Oliveros served up a homer to the first batter he faced as a September call-up.

Oliveras has always had a big fastball, averaging 94 miles per hour as a big leaguer before and after elbow surgery. He's also always had iffy control, with nearly four walks per nine innings in the minors. He made some minor strides with his control last season when a lot of pitchers see their walk rate rise after surgery, but there's still plenty of work to be done in terms of harnessing his raw stuff.

As a 27-year-old reliever Oliveros is stretching the definition of "prospect" and expectations should certainly be modest, but when someone with a mid-90s fastball averages more than 11 strikeouts per nine innings at Double-A and Triple-A he's generally worth an extended look. Unfortunately for Oliveros, because the Twins decided against overhauling their bullpen this offseason he faces an uphill battle for an Opening Day roster spot.

For a lengthy discussion about projecting the Opening Day roster, check out this week's "Gleeman and The Geek" episode.