By Andrew Simon

It didn't garner much attention last year when relievers Zach Duke and Pat Neshek signed Minor League contracts with the Brewers and Cardinals, respectively. Yet both non-roster Spring Training invitees made their clubs' Opening Day rosters, and both surpassed all reasonable expectations.

Duke, a former failed starter, changed his arm slot and pitch mix, producing a 2.45 ERA and 11.4 strikeouts per nine innings. Neshek rediscovered his fastball and increased his velocity on his way to an All-Star season that included a 1.87 ERA and 7.6 strikeout-to-walk ratio in 71 games, by far the sidearmer's best mark in the Majors since 2007. Those performances earned both pitchers multi-year contracts this offseason -- Duke with the White Sox and Neshek with the Astros.

Duke and Neshek weren't the only recipients of Minor League deals to make an impact in the big leagues last season. J.D. Martinez signed with the Tigers after the Astros released him late in camp. Using overhauled swing mechanics, he slugged 23 home runs with a .912 OPS in Detroit. Reliever Scott Atchison (Indians), outfielder Chris Coghlan (Cubs), infielder Justin Turner (Dodgers) and outfielder/DH Delmon Young (Orioles) were among the others to become important parts of their teams' rosters in 2014.

These success stories are difficult to predict, but each year, every club invites several non-roster veterans to camp, and a small handful make good on that opportunity. Here is a look at five of the more intriguing players to watch as this Spring Training progresses.

Jesse Crain, RHP, White Sox

PECOTA projection: 35 2/3 IP, 3.31 ERA, 1.27 WHIP, 39 K, 0.5 WARP
Reasons for optimism: track record, improved health

It wasn't long ago that Crain was a force out of the White Sox bullpen. From 2011-13, he posted a 2.10 ERA over 150 innings for the club, striking out 176 batters. But the 33-year-old hasn't pitched in a game in 20 months, thanks to a slow recovery from October 2013 biceps surgery.

It's impossible to know if Crain's arm will allow him to return to the mound, much less to his prior form. Yet reports early this spring have been positive, with Crain feeling well enough to include some sliders in his bullpen session on Wednesday. As long as he is able to get ready physically, whether it's for Opening Day or later in the season, Crain figures to get a chance to take on a prominent role in the Chicago bullpen. Though the club signed Duke and closer David Robertson this offseason, its relievers finished 28th in the Majors in ERA last year, and Crain should enjoy a comfort level in the organization due to his earlier time there.

Chris Parmelee, OF/1B, Orioles

PECOTA projection: 352 PA, .255 AVG, 10 HR, 42 RBI, 0.7 WARP
Reasons for optimism: youth, Minor League production

Parmelee ran out of chances with the Twins, who let him go after last season, his ninth in the organization. The 20th overall pick in the 2006 Draft, Parmelee has mastered the International League, where the left-handed hitter owns a .295/.395/.530 line and 27 homers over 141 games spanning the last three years. But after a promising 21-game debut in 2011, Parmelee was unable to establish himself in Minnesota, struggling to a .675 OPS in more than 800 plate appearances.

History is littered with hitters who never figured out how to bridge the huge gap between Triple-A and the Majors, but for some players, things can click a little later. Martinez, for example, was 26 last year, as was Chris Davis when his game started to come together for the Orioles in 2012. Heck, Baltimore got a breakout year from 31-year-old journeyman Steve Pearce last season. While it is far from guaranteed that Parmelee could take such a step, he did turn 27 on Tuesday and should get an opportunity sooner or later to show manager Buck Showalter what he can do.

Wandy Rodriguez, LHP, Braves

PECOTA projection: 78 2/3 IP, 3.76 ERA, 1.21 WHIP, 60 K, 0.5 WARP
Reasons for optimism: track record, improved health

From 2008-12, Rodriguez produced a 115 ERA+ while averaging 31 starts and 187 innings for the Astros and Pirates. Then the southpaw ran into health problems and has started only 18 games since while suffering from a forearm strain and a right knee problem that required surgery last June. That put an end to a season that was as ugly as it was short, with Rodriguez surrendering 37 hits and 10 homers in only 26 2/3 innings.

At age 36, time isn't on Rodriguez's side as he tries to get his career back on track in Atlanta. With that said, he impressed manager Fredi Gonzalez during a bullpen session on Tuesday, when Gonzalez declared Rodriguez healthy and said his arm was working well. It remains to be seen if that level of cooperation will continue, but if it does, Rodriguez seems to have as good a chance as anyone to claim the final spot in the Braves' starting rotation.

Pat Venditte, RHP/LHP, A's

PECOTA projection: 34 1/3 IP, 4.41 ERA, 1.43 WHIP, 30 K, 0.1 WARP
Reasons for optimism: Minor League production, organizational fit

It is impossible not to be intrigued by the prospect of an ambidextrous hurler taking on Major League hitters, and Venditte might have found the perfect place to put his rare skill set to the test. The 29-year-old joined Oakland after spending seven seasons working his way through the Yankees' system, putting up solid numbers but never receiving a promotion to New York.

Venditte comes to the A's with a 3.14 ERA and 200 strikeouts over 194 2/3 innings between Double-A and Triple-A. The natural right-hander has been throwing with both arms since age 3, developing an ability that should allow him to enjoy the platoon advantage in most situations. It's hard to think of an organization that would embrace such a player more than the A's, with manager Bob Melvin recently saying of Venditte, "He is in the right place."

Carlos Villanueva, RHP, Cardinals

PECOTA projection: 109 1/3 IP, 3.76 ERA, 1.21 WHIP, 96 K, 1.0 WARP
Reasons for optimism: Success as a reliever

It was a bit surprising to see Villanueva settle for a Minor League deal, which might seem like an odd thing to say about a 31-year-old who has produced an ERA above 4.00 for seven straight seasons. But a look at the righty's splits reveals two different pitchers. In 76 career starts, Villanueva owns a 5.00 ERA and 6.5 strikeouts per nine innings; in 314 relief appearances, the ERA drops to 3.55 while the strikeouts shoot up to 9.0 per nine.

The contrast is even more pronounced over the past four seasons, during which time Villanueva has posted a 2.64 ERA as a reliever, with 8.6 strikeouts per nine and a .214 opponents' average. Considering his lack of a platoon split and ability to eat multiple innings or even make an occasional spot start, Villanueva seems to be a good bet to contribute to the St. Louis bullpen.

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Andrew Simon is a contributor to Sports on Earth and a reporter for MLB.com.