Coming off 2015's disappointing performance, the 33-year-old southpaw showed new signs of life in 2016. It was a busy year for Duke, who pitched 61 innings over a career-high 81 games. While he wasn't labeled as a lefty specialist, he was especially dominant when facing left-handed hitters, against whom he finished the year with a 1.65 ERA and 1.10 WHIP. Although he raised his strikeout rate half a percent to 26.4, he had another year with an uncharacteristic lack of control, resulting in an 11.2 percent walk rate. Unfortunately, the Cardinals will have to look elsewhere for someone to replicate Duke's solid relief in the upcoming 2017 campaign, as he recently underwent Tommy John surgery and is going to be out for the entirety of the season.

The White Sox signed Duke prior to the 2015 season thinking he would be a slightly lesser version of Andrew Miller. Instead, they got a below-average left-handed reliever. He posted a 2.14 FIP for the Brewers in 2014, but that ballooned to 4.62 in 2015. His ERA jumped a full point despite a lower BABIP and increased strand rate. However, he struck out fewer guys, issued walks at a career high 4.8 BB/9 clip, and posted an absurd 24.3% HR/FB rate. If he can bring the walks down and keep the ball in the park, Duke may once again be an effective setup man. He will be asked to pitch the eighth inning for the White Sox in 2016 with the hope that he can more closely resemble his 2014 form.

Duke was not even guaranteed a roster spot when he signed a minor league deal with the Brewers last offseason, but that did not stop him from becoming one of the team’s best relievers. He was more than just a situational left-hander, as he fared well against both lefties (.569 OPS against) and righties (.586 OPS against). After his big 2014 season, Duke landed a three-year contract with the White Sox. He figures to factor into the late-inning mix as part of the bridge to new closer David Robertson.

Duke was slowed by a broken hand suffered in spring training and carried a 5.47 ERA after nine starts before losing his rotation spot for good in July. His results out of the bullpen were better, as he delivered a 3.86 ERA over 25.2 innings in relief. Unfortunately for Duke, he doesn't miss bats (2.1 K/9IP as a reliever) against right-handed hitters and his days as an option every fifth day are likely over. The D-Backs declined his 2012 option and made him a free agent in October, while the Astros took a chance on him with a one-year deal in December. If he fails to make the rotation, the Astros could try him in a LOOGY role as he maintained a 12:1 K:BB and .225 BAA against left-handed hitters in 2011.

A year removed from a surprising All-Star nod, Duke put together the worst season of his five-year major league career in 2010. The soft-tossing lefty compiled a 5.72 ERA, 1.654 WHIP and .321 BAA. Trouble with the long ball (25 in 159 innings) and an inability to throw strikes -- his 2.89 BB/9IP was a full-season worst -- doomed the pitcher with too few weapons in his arsenal. Moving to Arizona, it's hard to see how his numbers might improve at hitter friendly Chase Field. He doesn't strike out nearly enough batters for fantasy owners and the only category he's consistently excelled in is innings pitched. Getting out of Pittsburgh might put him in line for a couple more wins, but Duke should be available on plenty of waiver wires once the season starts.

Duke went from a down-trodden pitcher in 2008 to a decent hurler who simply pitches for a down-trodden franchise in 2009. He tied for the staff lead in victories (11) with Ross Ohlendorf en route to a surprising professional turnaround that actually gave fantasy owners a modicum of value. In the past three years, the sinker-ball throwing lefty has lowered his ERA from 5.53 to 4.82 to 4.06 and dropped his WHIP from 1.733 to 1.497 to 1.315. He hit bottom, perhaps, when the Pirates actually renewed his contract for $10,000 less prior to the 2008 season. Now that Duke appears to be on the road to become an average left-handed starting pitcher, his salary is due for a spike. Inevitably, this is the quickest way out of Pittsburgh. It wouldn't be surprising to see him dealt for prospects at some point. If and when that happens, his value ramps up as his wins total also figures to rise. In the meantime, look for Duke's numbers to hover somewhere close to where they were in 2009.

The fact that Duke's 2008 numbers -- 5-14, 4.82 ERA and 1.50 WHIP -- marked a huge improvement over his prior two seasons, just goes to show how far Duke has fallen since his 2005 rookie campaign (8-2, 1.81 ERA and 1.20 WHIP). The best thing about Duke might be that he takes the ball every fifth day. The worst thing is that he rarely brings home a win, going 18-37 the last three years. When Duke does well, he pitches to contact with a heavy sinkerball. He'll compete for a spot in the starting rotation in 2009 but his marginal fantasy value is even less in front of a rebuilding Pittsburgh offense

Duke went from Opening Day starter to a laughingstock in 2007. Opposing batters hit a whopping .359 off of the 24-year-old lefty, with Duke allowing 161 hits in 107.1 innings. He went 3-8 with a 5.53 ERA and 1.733 WHIP. Certainly it's natural for young pitchers to go through ups and downs to an extent, but Duke has swung to the extremes. He went 8-2 with a 1.81 ERA in 84.2 innings as a rookie in 2005. For that reason, there remains hope in Pittsburgh that Duke can find himself. Former pitching coach Jim Colborn, who Duke blamed for tinkering with his mechanics in spring training of 2006, is gone. Whether that helps Duke from a psychological standpoint remains to be seen. He'll compete for the team's fifth starter role in camp.

Duke epitomized the term "sophomore slump" in 2006. In his rookie campaign Duke breezed to an 8-2 record with a 1.81 ERA and 1.20 whip in 84.2 innings. Last year, he buckled under the pressure of being a No. 1 starter, going 10-15 with a 4.47 ERA and 1.50 whip in 215.1 innings. A closer look at his numbers reveal that Duke improved following the All-Star break. The 23-year-old lefty posted a 3.65 ERA in 98.2 innings after the Mid-Summer Classic. So long as Duke's arm doesn't fall off due to his workload he should see further improvement in 2007. Additionally, with Ian Snell establishing himself as a capable major league pitcher, Duke won't need to deal with the added pressure of being the staff ace.

Duke delivered far beyond anyone's expectations in 2005, going 8-2 for the Pirates after starting the season 12-3 for Triple-A Indianapolis. Savvy beyond his 23 years, Duke mixes a 93-mph fastball with a slider, changeup and a still-developing curve ball. His consistent mechanics and attention to detail set him apart from other hurlers his age. It's a bit unrealistic to expect Duke to perform at the rarefied level he achieved in 2005, but then again, he's been surprising folks ever since the Pirates stole him in the 20th round of the 2002 draft.

Duke, the Pirates’ Minor League Pitcher of the Year in 2004, split the season between high Single-A Lynchburg and Double-A Altoona, and led all Bucs’ minor-league pitchers in wins (15) and ERA (1.46) and was second in strikeouts (142). The lefty figures to begin the season at Triple-A Indianapolis, but he is a fast mover and his is definitely a name to file away for those in keeper leagues.