No. 4: '07—Homer Bailey; '17—Troy Tulowitzki

The Original No. 4: Bailey (No. 5 BA, No. 4 BP)

Tagged for a 6.72 ERA in 17 major league starts in 2007 and '08, Bailey finally got a foothold in the majors in mid-2009, but shoulder woes limited him to just 41 starts over the next two seasons. He put together a pair of strong, healthy years in 2012 and '13, punctuated by a pair of no-hitters. The Reds signed him to a six-year, $105 million contract in February 2014 but it has proved to be disastrous, as injuries have limited him to just 31 starts since, including eight in the last three seasons. 

The New No. 4 (Troy Tulowitzki (No. 15 BA, No. 24 BP)

Chosen seventh in the 2005 draft, Tulowitzki debuted in late '06 and helped the Rockies reach their first and still only World Series the following year. Despite his 24 homers, 31 Defensive Runs Saved and 6.8 WAR, he was robbed of the 2007 NL Rookie of the Year award by the Brewers' Ryan Braun, whose 34 homers and league-leading .631 slugging percentage were offset by-32 DRS at third base en route to just 2.0 WAR. With five All-Star appearance and two Gold Gloves, Tulo has been strong for both Colorado and Toronto, but durability issues—he’s topped 140 games just three times—and the Coors Field factor will limit his Cooperstown chances.