The Astros already own a 5 1/2-game lead in the American League West, yet they're looking to get better. Collin McHugh's return to the rotation this year began well but has resulted in 24 earned runs in 18 innings over his last four starts, so Houston seeks an alternative.

With one of the deepest farm systems in the game and a Triple-A Round Rock rotation full of prospects, the Astros have plenty of options. They're going to turn to right-hander Corbin Martin, a 2017 second-round pick who ranks No. 71 on MLB Pipeline's Top 100 Prospects list.

• Astros Top 30 Prospects

Martin has logged a 1.48 ERA in five outings at Round Rock this year, holding opponents to a .167 average while striking out 28 in 24 1/3 innings. Called up on Sunday, the 23-year-old right-hander immediately will move into McHugh's rotation slot and start this afternoon against the Rangers.

Martin has the best combination of stuff and polish among Houston's upper-level pitching prospects. He has a four-pitch arsenal highlighted by a 92-95 mph fastball that peaks at 97 with running action, and he has pushed his velocity into the upper 90s in shorter stints. Both of his breaking balls can miss bats as well, with his slider grading slightly better than his curveball.

As he has used his changeup more often in pro ball, it has become at least an average pitch and allowed Martin to keep left-handers in check. Recruited as a two-way player by Texas A&M, he's more athletic than most pitchers, which helps him repeat his delivery and maintain the quality of his stuff into the late innings.

Martin shuttled between the bullpen and rotation in college with the Aggies, and scouts thought he might take off once he got to pro ball and was kept in a consistent role. He has done exactly that since the Astros signed him for $1 million with a pick they received from the Cardinals as a punishment after former St. Louis scouting director Chris Correa was caught in a hacking scandal.

In three years at Texas A&M, Martin compiled a 4.01 ERA while averaging 4.8 walks and 10.1 strikeouts per nine innings and a .260 opponent batting average. As a pro, he owns a 2.31 ERA while averaging 2.8 free passes and 9.7 whiffs per nine innings and limiting hitters to a .190 average. He has improved his ability to command his fastball and throw strikes with his entire repertoire.

Martin worked a career-high 122 innings in 2018, and Houston probably will avoid a dramatic one-year increase in his workload. While he offers the potential for a mid-rotation starter, all the Astros need from him at this point is to provide competent innings every fifth day.

He's certainly capable of doing that. If Martin were to stick in Houston's rotation for the remainder of the season, he could win eight to 10 games while posting something along the lines of a 4.00 ERA and 100 strikeouts in 125 innings.