HOUSTON -- The Astros will enter this spring with one of the deepest rosters they've had in recent memory. They're a team with few questions marks and likely even fewer spots on the 25-man roster to be had, assuming everyone stays healthy.
Two weeks shy of pitchers and catchers reporting to West Palm Beach, Fla., the Astros have invited 18 non-roster players to camp, meaning there will be 58 players (40-man roster is full). The non-roster list is a sprinkle of a few veterans, as well as some top prospects and other Minor Leaguers.
Considering the Astros' depth, it's hard to envision a scenario in which a non-roster invitee cracks the Opening Day roster, but who would have thought pitcher Asher Wojciechowski would have made the Opening Day rotation two years ago? Injuries and underperformance open doors for others.
The one name to keep an eye on is hard-throwing right-hander Francis Martes. Ranked the Astros' top prospect by MLBPipeline.com, he also is rated No. 20 overall on the Top 100 Prospects list for 2017.
The 21-year-old should start the season in the rotation at Triple-A Fresno after going 9-6 with a 3.30 ERA in 25 games (22 starts) at Double-A Corpus Christi last year, with 131 strikeouts in 125 1/3 innings. Martes could find his way to Houston this year, and he'll have his first chance to impress the Major League coaching staff in the spring.
The outfield is crowded with George Springer, Josh Reddick, Jake Marisnick, Norichika Aoki and Carlos Beltran in the picture, but Derek Fisher -- the Astros' fourth-ranked prospect and 83rd overall -- has tools that could translate at the big league level. He hit .255 with 21 doubles, 21 homers, 76 RBIs, 28 steals and an .815 OPS in 129 combined games between Corpus Christi, where he was a Texas League All-Star, and Fresno (27 games).
Slugger Jon Singleton, the Astros' former top prospect, lost his spot on the 40-man roster in November and will come to camp trying to remain in the organization. It's going to be hard for manager A.J. Hinch to get him at-bats at first base with Yulieski Gurriel, A.J. Reed, Tyler White, Colin Moran and Marwin Gonzalez all vying for playing time, but Singleton's power earned him another look.

Lefty reliever Charles Riefenhauser, who made 29 appearances in the Cubs' Minor League system last year, topping out at Triple-A, could push for a spot. The Astros have been searching for a lefty to go along with Tony Sipp, though Kevin Chapman, Reymin Guduan and Ashur Tolliver are also lefties on the 40-man.
Riefenhauser, infielder Reid Brignac and catcher Juan Centeno could all provide depth at some point this season. Brignac, who has appeared in big league games in each of the last nine seasons, spent the majority of his 2016 campaign with Triple-A Gwinnett in Atlanta's system, hitting .264 with 21 doubles, eight home runs and 42 RBIs in 102 games. Centeno spent 55 games as the Twins' backup catcher.