Thomas, 22, was initially promoted to the big leagues in May while considered one of the top prospects in the sport at the time. Baseball America, MLB Pipeline and FanGraphs all had him in the top 40 on their respective lists of the best youngsters around the league. Unfortunately, he hasn’t hit the ground running in his first shot at the big leagues, producing a batting line of .231/.275/.344 through his first 113 games for a wRC+ of 71, or 29% below league average.
He’s managed to keep the strikeouts down to a rate of 18%, which is a few ticks below the 22.3% league average this year. However, he’s also walked at a below-average 5.4% rate and isn’t doing much damage when he makes contact. His .263 batting average on balls in play could involve some bad luck, but he’s also in just the 21st percentile in terms of hard hit percentage, the 12th percentile for barrel rate and 20th in average exit velocity. He is in the 75th percentile in terms of max exit velocity, which suggests he can do damage when he does square the ball up. He’s just not doing it very often so far.
It’s not all doom and gloom, as Thomas has a solid floor because of his speed and defense. He has 94th percentile sprint speed and is in the 92nd percentile in terms of Outs Above Average. If the bat can take a step forward and start to resemble his production in the minor leagues, he would become an incredibly valuable and well-rounded player.
The Diamondbacks are flush with outfielders, which is seemingly what has nudged Thomas out of the picture for now. Daulton Varsho has seemingly made a permanent move from catching to the outfield, according to reporting from earlier this month. He joins an outfield mix that includes Thomas, McCarthy, Stone Garrett, Jordan Luplow and Corbin Carroll. Like Thomas, Carroll was a highly-touted prospect who made his debut this year, but with much more success. Through 24 games, Carroll is hitting .256/.318/.474 for a wRC+ of 119. With Varsho, Garrett and McCarthy all also hitting well, the club has a bevy of outfield options at its disposal at the moment.
The Diamondbacks are well out of contention with just over a week left in the regular season, meaning the remaining games will primarily be for evaluating players and gathering information for the future. In that context, it’s noteworthy that Thomas has been squeezed out here. During the offseason, there figures to be plenty of speculation about the club using its strong outfield depth to upgrade other parts of the roster, with varying opinions about who is most likely to be moved. This demotion certainly doesn’t mean Thomas has been erased from the team’s plans, as he’s still only 22 years old and prospects don’t always develop in a linear fashion. Though it does perhaps indicate that some less-hyped outfielders like McCarthy and Garrett have played well enough to earn longer looks and complicate the picture. McCarthy is hitting .288/.352/.446 this year for a 124 wRC+ in 91 games. Garrett has gotten into just 22 games but has hit .318/.352/.621 in that time for a wRC+ of 165.
From a service time perspective, this won’t have an immediate impact on Thomas. He was promoted a month after Opening Day and was always going to come up short of one year of service time in 2022. This demotion, assuming he doesn’t return, will only cost him about ten days from his tally. (Optional assignments for position players come with a ten-day minimum but an exception is made if another player is going on the injured list.) Though if Thomas continues to be outside the team’s immediate outfield plans, future optional assignments could push back his free agency or arbitration eligibility.