SCOTTSDALE, Ariz. -- With lefty Chris Rusin (upper-back discomfort) and righty Antonio Senzatela (right heel infection) unlikely to be ready for the start of the regular season, the Rockies seemingly have two bullpen spots for which three pitchers are competing.

The Rockies are expected to have an eight-man bullpen when they open the season on March 28 in Miami. Barring other injuries, they have six penciled in -- righty closer Wade Davis, fellow righties Scott Oberg, Seunghwan Oh and Bryan Shaw, and lefties Mike Dunn and Jake McGee.

Manager Bud Black said on Sunday morning that while Senzatela could be ramped up to throw in the bullpen, it’s better to prepare him to start at Triple-A Albuquerque, and be part of the depth picture. Black added that starter-types not in the projected rotation are better off working at Albuquerque than waiting in the Rockies’ bullpen for opportunities.

That would leave a race for two spots among lefty Harrison Musgrave and righties Carlos Estévez and DJ Johnson. All are on the 40-man roster and can be optioned to the Minors without having to be exposed to waivers.

Here is a look at each candidate:

Musgrave: A starter until being converted to the bullpen when debuting in the Majors last season, the 27-year-old Musgrave is not a big strikeout threat (32 in 44 2/3 innings last season over 35 appearances), but his strike-zone performance this spring has been solid. To reach full potential he’ll have to refine his two-seam fastball and hone it into a pitch that forces weak contact.

On Sunday against the Cubs, Musgrave struck out two but gave up one big hit -- a Johnny Field home run.

“I was pretty confident after what happened last year,” said Musgrave, who was on the postseason roster and allowed one run while recording a pair of outs over two appearances. “You’ve got to look at what happened and go from there. I’ve thrown a lot of strikes and worked on what I want to.”

Estevez: After missing last season with injuries -- first a left oblique strain, then a right elbow strain -- Estevez has been electric at times this spring. He has 11 strikeouts in seven innings this spring, but also five walks. His ability to hit targets will be big in his evaluation.

It’s been a long climb back for Estevez, who had 11 saves as a rookie in 2016 and pitched well enough at the end of '17 to make the postseason roster. He entered Spring Training healthy and confident, with a more controlled motion.

“Now it doesn’t look like I’m fast with my body, but my arm is late -- everything looks compact and going at the same time,” Estevez said.

Johnson: After bouncing to four organizations and playing independent ball, Johnson made the Majors last September and earned a postseason roster spot. This spring, Johnson (five strikeouts, one walk, three hits in 6 2/3 scoreless innings) is confidently displaying a unique mix of a low-90s fastball and myriad pitches that make him diverse as a reliever.

“I’ve always been a fastball-breaking ball guy. I developed my cutter in 2017, [but] kind of went away from it last year,” Johnson said. “I’ve always had fun trying out new pitches, learning new pitches. It’s always good to have extra weapons.

“One thing that’s eluded me is a changeup, as hard as I try. I’ve been fiddling with that a little this spring. It’s fun for me. I always have a baseball in my hand, messing around with different grips and trying to manipulate the ball different ways.”t