Throughout the 2021 season, there have been few Astros prospects as consistently locked in at the plate as outfielder Marty Costes. He opened his campaign at Double-A Corpus Christi, and was a dynamic top of the order threat for the club over the duration of his stay. hitting .332/.436/.409 while patrolling the outfield. That would earn him a promotion to Triple-A Sugar Land, where his performance has improved further to a .299/.417/.517. His strike zone discipline is perhaps his best trait, and it has stood out at both stops, but you’ll notice that his power has ticked up significantly since the promotion— this is a very positive development for any player, but particularly one with Costes’ background, so let’s dig into it a bit.
Costes was really never a high profile amateur player. A native of Baltimore, he played prep ball in his hometown at Archbishop Curley, which is yet to produce a big league ballplayer. His unique 5’9” build with limited speed made projecting him defensively a challenge, and there wasn’t a high enough level of prep competition for teams to feel fully confident in the bat at this point. Despite not playing in a hotbed, Costes was able to garner some positive attention for his play, even if it wasn’t at the pro level, and took an offer to continue his career at the University of Maryland.
To tune up for his freshman campaign with the Terps, Costes played in the Cal Ripken Collegiate League, a Maryland-based offseason league. He performed well against competition about older than him, hitting .276/.356/.438 in 34 games with a 16/10 K/BB ratio. That gave him a bit of momentum entering 2016, and he’d capitalize by seizing a beefy freshman role, hitting .263/.363/.479 with 9 home runs, which led the Terrapins. He’d return to the CRCL the following offseason, where he hit .319/.438/.560 with another 7 bombs.
As a sophomore, Costes seemed to take at least a bit of a step forward. Starting 61 games, he hit .322/.429/.548, again leading the team in home runs with 13. A draft eligible sophomore, there was some serious interest from pro clubs at this point, but it was limited to a degree by defensive question marks. Costes felt that he could improve his stock further, and, seeking a new challenge, he opted for the Cape Cod League after the season rather than a return to the Ripken League. Despite a big step up in competition, Costes seemed well equipped to handle CCBL pitching. He got into 32 games for Brewster that summer, hitting .293/.427/.511 with 5 bombs and a 20/16 K/BB mark.
A Cape performance like that will provide a major boost to anyone’s stock, and Costes was no different. With two outstanding college seasons under his belt and a strong Cape performance to match, it looked like he had a strong chance to become a day two draft pick despite some athletic limitations. Unfortunately, it would not go according to plan, as Costes’ power all but disappeared that season. There were some nagging injury issues that limited him to 50 games, but that didn’t fully explain his backslide to a .235/.382/.374 line in the eyes of teams. The strike zone discipline was still there in full force, but the lack of defensive value combined with a concerning power outage torpedoed his stock.
This was obviously a highly disappointing development for Costes, but worked in the Astros’ favor, as they were able to snag him very late in the 2018 draft, coming away with him in the 22nd round. He signed immediately and got a 53-game debut in right away, mostly with Low-A Quad Cities. He’d hit .243/.360/.387 there, roughly in line with his college performance earlier that year. As a result, he’d enter 2019 as something of an enigma. The raw power that he used to lead his college club in homers twice was still in there, as he’d frequently post some upper echelon exit velocities, but he was struggling to lift the ball, sporting very high ground ball and infield fly ball rates.
The Astros decided to re-assign him to Low-A Quad Cities to open 2019, where he was older than his competition at this point, and while his surface numbers improved significantly to .291/.378/.456, there were still some big red flags in the batted ball department, with a ground ball rate north of 50. Nonetheless, the Astros decided to bump him up to a more age appropriate level (A+) for the 2019 stretch run, where he hit .247/.362/.371. Obviously, there was still a lack of extra base power, though again, it wasn’t for a lack of raw.
Costes had little attention entering 2020, which became doubly true when the minor league season was cancelled thanks to COVID-19. Despite the low profile though, Costes’ statistical profile indicated that a breakout could be still be a possibility. He remained a corner-bound player defensively without the requisite power, but evaluators mining the deepest parts of the minor league player pool remained intrigued by his unique blend of plus strike zone command as well as raw power that, based on pure exit velocity, was borderline double-plus. If the Astros and Costes could collaborate on some adjustments to help him lift the ball more regularly, the major league offensive bar was within reach, even in an outfield corner.
There was little info on Costes during the 2020 shutdown, but one would assume that his focus was on plane-related adjustments as alluded to above. Entering 2021, he’d remain on the fringes of the radar, but quickly started to garner a bit more attention when the season got underway. Making the leap to Double-A after a year away from live game action, Costes rapidly settled in as one of the Hooks’ best hitters. Serving as the every day right fielder when healthy, Costes hit a red hot .332/.436/.409. While there was still far too much contact on the ground at 50.6%, he was consistently hitting the ball hard, including a significant jump in line drive rate, and to manage a 17% K rate in his first taste of the upper minors was impressive.
While still hoping to see more elevation, the Astros were satisfied with his progress and bumped him up to Triple-A Sugar Land, where he has shown some more signs of perhaps rediscovering his pop from his college days. Currently hitting .299/.417/.517, Costes has already managed 3 home runs in 29 games since the promotion, more than he had in his 61 games with Corpus. While his groundball rate remains on the wrong side of 50%, which is a stratospheric figure, his usually sky-high infield fly rate has dipped all the way to 4.8%. This appears to be the primary driver behind his ISO nearly tripling between the two levels, and it’s also worth noting that his Triple-A bombs have been far from cheapies. His first homer was this moonshot at Dell Diamond:
TOUCH 'EM ALL!!— Sugar Land Skeeters (@SL_Skeeters) August 11, 2021
Marty Costes hits his first Triple A homer and it went ... *check notes* ... 458 feet pic.twitter.com/hjziUwwovs
This was perhaps Costes’ biggest bomb in years, but he made it clear that he wasn’t satisfied when he hit an even more impressive jack a few weeks later, this time in the friendly-but-homer-suppressing confines of Constellation Field:
While minor league statcast data isn’t always completely reliable— hell, even big league data can err occasionally— that exit velocity is not a typo, and should be all the evidence that anyone needs of his prodigious raw power. It’s especially eyebrow-raising when considering Costes’ sub-5’10” height— there are disadvantages to a smaller frame to be sure, but it’s also a benefit in many ways at the plate as far as making contact is concerned, as it creates a smaller zone and shorter levers tend to counteract swing and miss. It’s rare to see 115 EV pop in a package this size, which makes Costes all the more intriguing.
These tastes of over the fence power have been tantalizing, as Costes’ offensive profile would have few holes remaining if he were able to get to his pop with a bit more regularity. He’s still not quite hitting like a slugger, but the near-elimination of infield flies over the last month has piqued a lot of interest. Costes’ swing plane is such that he’s likely to continue to produce more grounders than is ideal, and we shouldn’t expect him to completely revolutionize his batted ball profile, as such things are only so mutable, but the progress is definitely a welcome sight. As said above, there’s really only one obstacle between Costes and a productive big league future, and while it’s a tricky one to clear, it’s also an area where older prospects like Costes tend to have a puncher’s chance to improve. He’s far from a prototype, but between his command of the zone and his explosive rotational power, he has some tools in his bag that few other player can claim, and is more than deserving of a close eye going forward.