SCOTTSDALE, Ariz. -- Ryan McMahon made sure there was room for him.
Before Tuesday's Spring Training finale against the Mariners, Rockies manager Bud Black informed McMahon -- the Rockies' No. 2 prospect and No. 41 overall according to MLB Pipeline -- that he has made his first Opening Day roster.
Last year combined at Double-A Hartford and Triple-A Albuquerque, the left-handed-hitting McMahon hit a combined .355 with 39 doubles, four triples, 20 home runs and 88 RBIs before going 3-for-19 in a 17-game taste of the Majors.
It wasn't clear there would be a place for McMahon, 23, on a roster crowded with veterans. But the Rockies couldn't deny him after seeing him compile a .328 batting average and a .912 OPS, with two home runs and nine RBIs in 67 Cactus League at-bats.
:: Spring Training coverage presented by Camping World ::
"I wanted to show how I've matured in my game, my new approach, how I execute that," said McMahon, who had gone 1-fo-29 over the previous three Spring Trainings. "I think I did well. The guys believe in me. The coaches believe in me. So I'm excited for the season."
Playing time will likely come at first base, with Ian Desmond -- who will be on the field regularly during the second year of a five-year, $70 million contract -- moving to left field and Gerardo Parra becoming a bench player on days McMahon starts.
McMahon, who was drafted in the second round in 2013 as a third baseman and has filled in at second during his pro career, also will likely be called upon for pinch-hit duty.
"I came to show what I was about, show that I'm here to work, play hard and play some good ball along the way," McMahon said.
When Carlos Gonzalez re-signed earlier this month, Black played Desmond consistently at first base, while McMahon squeezed in starts at third and came off the bench. McMahon showed enough to convince the Rockies that he could handle such duty, and he could earn more playing time if the power he displayed last year translates to the Majors.
Video: McMahon on his spring, Black on slugger's approach
"I think I'll be able to do whatever they ask me to do," McMahon said. "And I've got to stay ready, because I don't make the decisions. Bud Black does. Just stay ready and keep doing what I'm doing."
The move became clear when the Rockies optioned outfielder Raimel Tapia, who contributed off the bench last season while bouncing between Triple-A and the Majors, back to Albuquerque. While Tapia receives regular at-bats in Albuquerque -- along with David Dahl, another highly touted outfielder -- McMahon will get his big league chance.
With the roster not set in stone until Thursday, Black did not announce McMahon as a member of the 25-man roster officially, but said he has useful tools and "is becoming a confident, mature player."
With that decision, the roster is beginning to fall into place:
• Left-handed-hitting outfielder Mike Tauchman, the Rockies' Abby Greer Award winner as Spring Training Most Valuable Player, will join McMahon and catcher Tony Wolters as left-handed hitters on a four-man bench. The Rockies also optioned catcher Tom Murphy to Albuquerque on Tuesday.
Infielder Pat Valaika, who batted .328 (19-for-58) with 12 runs, eight doubles, four homers and 16 RBIs as a pinch-hitter last season, is the righty bat off the bench.
• As Black has hinted at over the last several days, right-handed Antonio Senzatela, a starter by trade, will be carried in the bullpen to begin the season. Senzatela has 1.62 ERA in five Cactus League games.
• Reliever Zac Rosscup has been trying to make the team as a lefty specialist, but hasn't appeared in a Cactus League game since March 14. Black said after Tuesday's game that he has an issue with his left middle finger. Rosscup, who is out of Minor League options, can begin the year on the disabled list, which would open a spot for Senzatela.
• Righty reliever Carlos Estevez (left oblique strain) and righty starter Jeff Hoffman (right shoulder inflammation) will begin the season on the 10-day disabled list. Righty reliever Rayan Gonzalez (recovery from Tommy John right elbow surgery) is on the 60-day DL.
In a three-inning tuneup on Tuesday, Rockies righty Chad Bettis struck out two and forced three ground-ball outs, while giving up one run on two hits and a walk.
"Really, it was a mix of everything; it was not just one pitch, which benefits me," said Bettis, who is in line to pitch Monday, the first of four games in San Diego. "I accomplished what I wanted today, redefining command, getting a little sharper."
Although the rotation has been set for some time, Black officially announced his starters for the season-opening series at Chase Field vs. the D-backs -- righty Jon Gray on Thursday night, lefty Tyler Anderson on Friday night and righty German Marquez on Saturday night.
Thomas Harding has covered the Rockies since 2000, and for MLB.com since 2002. Follow him on Twitter and like his Facebook page.