MLB.com Columnist

Jonathan Mayo

What to expect: McCullers makes MLB debut

Astros' No. 10 prospect sure to feature electric stuff, but can he keep his command?

What to expect: McCullers makes MLB debut

Lance McCullers is making the jump from Double-A Corpus Christi to Houston, and he will be making his Major League debut on Monday night. The right-hander has always been blessed with electric pure stuff, but he hasn't always been able to harness it. Improvements in that area have allowed McCullers to take a major step forward to the point where the Astros felt he was ready to make the double leap to Minute Maid Park.

The Astros' No. 10 prospect was one of the key acquisitions in the organization's 2012 First-Year Player Draft strategy. Houston took Carlos Correa No. 1 in what seemed like a bit of a reach at the time (not so much now), saving money that allowed the club to draft and sign McCullers at No. 41 overall as well as the since-traded Rio Ruiz in the fourth round, both for well over pick value.

McCullers is the son of the former big league reliever of the same name, and many felt the younger McCullers was also destined for a career in the bullpen because of effort in his delivery and a lack of command (he walked 5.2 per nine during a rough 2014 season). But it seems like something clicked this year on a number of fronts.

Top Prospects: McCullers, HOU

McCullers' stuff has always been there and remains as good as it ever was, with a fastball that touches the upper 90s mph and a hammer curve. But now he's throwing a ton more strikes. McCullers' walk rate is down to 3.4 per nine while not missing a beat on the missed bats front (13.3 K/9, which is well above his career rate of 10.7). Broken down another way, he has a 37.1 strikeout percentage (vs. 26.4 in 2014) and is walking just 9.5 percent (compared to 12.8 a year ago).

In addition to McCullers' newfound relationship with the strike zone, perhaps the biggest improvement has been with his offspeed stuff. His changeup has come a long way, sometimes even showing flashes of being an above-average pitch.

McCullers is going to need that third pitch to have success at the highest level, though his fastball-curve combination is good enough to get hitters out at any level, at least the first time around. Remember, this isn't a club trying out guys for the future. The Astros sit atop the American League West and believe McCullers can help them stay there now. He'll have to show an ability to make adjustments, mix his pitches and stay within himself to do that long-term.

It stands to reason that the 21-year-old might be a bit amped up to start things off, which could make McCullers overthrow a bit and lose some of his improved feel for pitching. But look for him to settle down and give Houston a boost and an upgrade at the back end of the rotation. Long-term, as long as the command is there, McCullers has everything a team wants in a front-line starter.

Jonathan Mayo is a reporter for MLBPipeline.com and writes a blog, B3. Follow @JonathanMayoB3 on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.