First base is a position of strength for the Colorado Rockies. Justin Morneau signed a modest two-year, $12.5-million contract in Dec. 2013 and won the National League batting title in his first year with the Rockies. Morneau, entering his age-34 season, is a bargain this year -- and the Rockies hold a reasonable $9 million option for 2016 as well.
Even with a short trip to the disabled list for a neck strain, Morneau started 126 games, played in 135, and amassed 550 plate appearances. Morneau doesn't need many days off, although his platoon splits in 2014 (.254/.288/.377 vs. lefties and .341/.389/.538 against righties) might inspire manager Walt Weiss to rest Morneau against left-handers more often.
Catcher Wilin Rosario worked at first base, and the corner outfield positions, during the winter in hopes of turning him into more of a super utility player. If the right-handed batting Rosario is able to handle the position defensively, he'd be a natural replacement for the rare times Morneau doesn't start. Reserve infielder Charlie Culberson is also capable of playing first base occasionally, but not every day if Morneau went on the disabled list.
Who plays first base for the Isotopes depends on who the Rockies keep as reserves.
Paulsen's biggest problem is that he's left-handed in a left-handed heavy lineup. Morneau is a lefty. The projected starting outfield of Corey Dickerson, Charlie Blackmon and Carlos Gonzalez are all left-handed. Likely outfield reserves Drew Stubbs and Brandon Barnes are both right-handed hitters.
If Paulsen doesn't win a backup job in the majors, he'll be anchoring the middle of the Isotopes lineup. In all likelihood, he'll be shuttled between Denver and Albuquerque, based on injuries and performances.
Parker is coming off his worst year, however, and fell out of BA's Top 10 list. His slash numbers of .289/.336/.450 in 542 plate appearances for triple-A Colorado Springs were solid, but it was reasonable to expect more from an elite prospect playing at one of the most hitter-friendly ballparks in the country. Parker's on-base percentage has dropped the last three years (.415 to .345 to .336), along with his slugging percentage (.562 to .492 to .450).
Still, Parker is two years younger than Paulsen. He's played mostly the corner outfield positions in the minors, but started 40 games at first base last year for the Sky Sox and two for the Rockies. In his 26 at-bats in the majors, Parker had four singles, one double and 14 strikeouts. It's a small sample size, no doubt, but it probably means Parker will repeat Triple-A in 2015.
Ryan Casteel was the leader in games played at first base for the Rockies' double-A affiliate in Tulsa last year. The next closest was Harold Riggins, at 46 games, and he's no longer in the organization.
Casteel is a catcher-first base hybrid who has played one full, entire season at every level in the Rockies chain, since getting drafted in the 17th round in 2010 out of Cleveland State. Casteel slashed .280/.341/.445 last year, and his versatility gives him value.
Jordan Ribera was the primary first baseman at high-A Modesto. Ribera was repeating that level, slashed a pedestrian .257/.324/.382, and already entering his age-26 season in 2015.
As mentioned in the catchers preview, it's possible the Rockies keep three catchers in the majors and triple-A. That would be very unique, but Rosario and Casteel's flexibility makes it worth considering.
In summary, expect to see Paulsen, Parker and Casteel playing first base at various times for the Isotopes in 2015. Paulsen and Parker should also see time at the corner outfield spots, while Casteel gets time behind home plate.