SCOTTSDALE, Ariz. -- Teams show up at Spring Training with a to-do list. But as Rockies manager Walt Weiss noted, sometimes it grows.

When camp started, one starting rotation spot was open for a challenge, with right-hander Juan Nicasio the incumbent. But at the start of this week, right-handed stalwart Jhoulys Chacin experienced a strain and inflammation in his throwing shoulder. He is prohibited from throwing until the training staff checks with him this weekend or early next week, and it's possible he won't break camp with the team.

So, add another starter to the Rockies' agenda, which also includes determining a starting center fielder and piecing together what will be a leadoff puzzle, before the March 31 season opener on the road against the Marlins. The process begins Friday afternoon with the Rockies' Cactus League opener, against the D-backs (live on Gameday Audio at 1:10 MT), with left-handed rotation competitor Franklin Morales starting.

"Now with Jhoulys' situation, we've got to be thinking about that, so absolutely there's some competition for a couple of spots," Weiss said Thursday.

Of course, the Rockies' hopes depend largely on the health of their key players.

Left fielder Carlos Gonzalez and shortstop Troy Tulowitzki missed time with injuries last season, and right fielder Michael Cuddyer won the National League batting title last year but missed time in 2012. Justin Morneau, signed for two years at $12.5 million to replace Todd Helton at first base, played 154 games last season with the Twins and Pirates after years of being affected by the aftermath of a 2010 concussion. The further development of catcher Wilin Rosario, who leads Major League catchers with 49 homers the last two seasons, and third baseman Nolan Arenado, who won a Rawlings Gold Glove as a rookie and is expected to develop offensively, will be big stories.

But those situations will play out over time. Spring Training is for decisions on the roster.

Morales, 27, started for the Rockies when he debuted in 2007, but moved to the bullpen long before he was traded to the Red Sox in 2011 and has pitched mostly in relief. However, Morales pitched this winter in Venezuela to positive reviews.

Righty Jordan Lyles, 23, who has pitched parts of three seasons with the Astros and was part of the deal that sent center fielder Dexter Fowler to Houston, will try to make his impression Saturday against the Reds in Goodyear. Lefty Christian Friedrich, 26, the team's top Draft pick in 2008, will make his spring debut Monday night in a split-squad game against the D-backs at Salt River Fields at Talking Stick.

The Rockies haven't even counted out their fast movers, right-handers Jon Gray, the club's top pick and third overall last year, and Eddie Butler, a supplemental first-rounder in 2012. Both 22-year-olds will pitch Monday -- Gray in relief against the Mariners at Peoria at 1:05 p.m. MT and Butler in relief that night against the D-backs. Also, there is non-roster candidate lefty Pedro Hernandez, who turns 25 on April 12 and made 14 appearances (12 starts) last season for the Twins.

The center-field situation is partially connected to the attempt to find a leadoff hitter.

But it's not fully connected because the roster doesn't present an obvious leadoff hitter, so Weiss wants his order flexible.

"I'm not too concerned about finding that guy, because our lineup tends to change," Weiss said. "Whoever we put in that spot I think will be capable of getting on base and playing that role. I'm not too concerned about finding one guy. We have multiple options."

Right-handed-hitting Drew Stubbs was a regular in center for the Reds from 2009-11, and spent last season in right with the Indians. He has leadoff speed, but has struggled with strikeouts and has power that would profile lower in the order. Although Weiss hasn't ruled out him batting first, he has said Stubbs may fit just behind the heart of the order. That could mean leadoff at-bats for second baseman DJ LeMahieu, who himself must fend off a challenge from Josh Rutledge.

LeMahieu hit .280 and had 18 steals last season. He has a .314 on-base percentage in 227 Major League games, but he had a .361 OBP in the Minors. LeMahieu is a good bat-handler -- seven sacrifice bunts and three sac flies last year -- who also profiles lower in the order.

"In this lineup, it's a great spot in the order because you've got so many great hitters coming up behind you," said LeMahieu, who earns high marks from the Rockies' coaching staff for his smarts on the bases. "It's going to be a big spot. I'm going to be the same hitter no matter where I am. I'm always going to be aggressive, trying to put together tough at-bats for the pitcher. Personally, if I'm leadoff, I'm going to treat it the same as when I'm anywhere else."

Where it gets really interesting is if the Rockies go with one of their left-handed hitters -- Charlie Blackmon, 27, or Corey Dickerson, 24, in center, both of whom played well after spending part of last season at Triple-A Colorado Springs. Blackmon hit .309 with six home runs and 17 doubles among his 25 extra-base hits and 22 RBIs in 82 games last season. Dickerson hit .263 with five homers, 17 RBIs and five triples among his 23 extra-base hits last year in 69 contests.

Based on their statistical sample sizes, both are comfortable enough to hit against righties and lefties. Blackmon has played more center field, but Dickerson has shown signs of being a fast learner.

Both also aren't opposed to batting leadoff.

There's also right-handed-hitting Brandon Barnes, 27, who hit .240 for the Astros in regular center-field duty last season and prides himself on moving runners. Also, Jason Pridie, 30, who has played with the Twins, Mets, Phillies and Orioles, is in the mix as a non-roster candidate.