These 5 pitchers are budding NL Central aces

Whether contending for a World Series right away or restocking the farm and building the next great roster, unearthing an ace is essential. That explains the age-old baseball adage: When you think you have enough pitching, go get more.

As part of our weekly look at the National League Central, MLB.com is looking at some of the future aces for each team. Here are our reporters' picks for the arm that could be leading each team's respective rotation for years to come, either as soon as the next season or down the road.

Brewers: Corbin Burnes

Burnes had as bad a year in 2019 as a pitcher can have. He allowed 11 home runs in 17 2/3 innings before the end of April. He ranked in MLB's 22nd percentile, according to Statcast, in exit velocity and in the bottom 20 percent in hard-hit percentage, expected weighted on-base percentage, expected batting average and expected slugging percentage. He was demoted first to Triple-A, then sent to the Brewers' pitching lab in Phoenix to figure out what was wrong.

So, how is he on a list of future aces?

He's only 25, and his stuff is ace-caliber. Burnes' 95.2 mph average fastball puts him in the 80th percentile, and his spin numbers are elite. Of the 392 pitchers who threw at least 200 four-seam fastballs last season, Burnes average spin rate of 2,656 rpm ranked second. And of 229 pitchers who threw at least 200 sliders, Burnes' average spin rate of 2,850 rpm was 12th. The tools are there to be a top starting pitcher. --Adam McCalvy

Cardinals: Jack Flaherty

There's an argument to be made that Flaherty arrived as the Cardinals' ace during his historic second half last season, when he posted a 0.91 ERA after the All-Star break. After a fourth-place NL Cy Young Award finish, the 24-year-old right-hander was set to be the Opening Day starter to begin his third full season in the Majors. He has often cited the guidance he's received from other club aces such as Adam Wainwright, Chris Carpenter and Hall of Famer Bob Gibson.

But Flaherty might be the first to tell you the ways he could improve. He mentioned it in the offseason and throughout Spring Training: His goal was to stay consistent during the year.

Flaherty had a 4.64 ERA in the first half last year compared to that tidy ERA post-All-Star break. The next level isn't about going higher than his second half last season, but to try to stay constant during the entirety of the season. Flaherty emerged as the Cardinals' future ace last season. Now the Cardinals are looking for him to stay on that path. --Anne Rogers

Cubs: Brailyn Marquez

The Cubs' recipe for building the core that grew into a World Series-winning group in 2016 has been well-documented. Chicago filled the foundation with polished position-player prospects and then went about finding arms via trades and free agency. The result has been a lack of homegrown pitchers reaching the Majors and making a major impact.

There are some promising arms in the pipeline now, but the most intriguing prospect with ace potential is by far Marquez (No. 2 on the Cubs' Top 30 list and No. 68 on MLB Pipeline's Top 100 rankings). The 6-foot-4 lefty (signed as an international free-agent in '15) has grown into one of the Minor Leagues' most powerful arms, hitting triple digits regularly and topping out at 102 mph in 2019.

Marquez certainly looked like a future ace last July 25, when he struck out 14 in six shutout innings against Class A Lake County. Including that outing for Class A South Bend, the lefty spun a 1.17 ERA with 48 strikeouts against eight walks in his last seven starts (38 1/3 innings), including five following a promotion to Class A Advanced Myrtle Beach. --Jordan Bastian

Pirates: Mitch Keller

Ignore last year's surface-level statistics for a moment, if you can. Remember Keller's excellent performance in the Minor Leagues? A refresher: He recorded a 3.12 ERA and 1.16 WHIP with a 3.33 strikeout-to-walk ratio from 2014-19, and he did so convincingly enough to consistently register as one of the top 50 prospects in baseball over the past three years. Amid his struggles in the Majors, he struck out 28.6 percent of the batters he faced and walked only 7 percent.

The 6-foot-2 right-hander, who turns 24 on Saturday, still has that front-of-the-rotation potential. And he knows it, too. Whenever baseball returns, it's easy to imagine Keller taking a massive step forward just due to better pitch-sequencing and anything less than the catastrophically bad batted-ball luck he endured last season. Working with pitching coach Oscar Marin and bullpen coach Justin Meccage, Keller learned this spring how to make better use of his fastball, slider and curveball.

Simply put, Keller is much better than last year's back-of-the-baseball-card numbers -- his 1-5 record and 7.13 ERA in 11 starts -- would indicate. As he told MLB.com in February, "Ultimately, one day I want to be the ace, so that's what I'm trying to be right now." --Adam Berry

Reds: Hunter Greene

During the 2018 SiriusXM All-Star Futures Game in Washington, all 19 pitches Greene threw registered at 100 mph or faster and his top velocity was 103.1 mph. But throwing that hard cost him, as he went down with an ulnar collateral ligament strain a couple of weeks later while pitching for Class A Dayton.

Rehabbing the injury without an operation failed when Greene tore the ligament during Spring Training and had Tommy John surgery in April 2019. The No. 2 overall pick in the '17 MLB Draft, Greene is still ranked the club's No. 2 prospect and No. 53 overall by MLB Pipeline.

The good news for Greene is his rehab from surgery had been going well before the shutdown of baseball, and he was on track to pitch competitively some time during the 2020 season. Cincinnati will obviously be extra cautious with the 20-year-old right-hander. But the hope is that fully healthy, Greene still has a strong chance at being a front-of-the-rotation starting pitcher. --Mark Sheldon