This article is part of a series chronicling the individual seasons of players that appeared for the Arizona Diamondbacks in 2024.

Reviews for players that still have rookie eligibility for 2025 will appear in our prospect season reviews. Players are presented in the reverse order of their aWAR, an average of Baseball Reference and FanGraphs WAR.

2024 Contract Status: Pre-Arbitration, $748,300, prorated to $48,276 for time on MLB roster

As the Diamondbacks’ bullpen settled into their roles in the 2023 season, hard-throwing righty Luis Frias was one of the relievers on the bubble.

While he had looked to be developing a bit in 2023, pitching to a serviceable (if not spectacular) 4.06 ERA over 31.0 innings, he never really had the chance to show his potential in 2024.

He made just seven appearances for the D-backs this season, giving up runs in four of them. On April 16, he surrendered a walk and two hits, leading to three earned runs without recording an out against the Chicago Cubs.

That resulted in a 9.95 ERA with the D-backs, although his 4.90 FIP suggested he was pitching somewhat better than his raw results, though not to a level that would be considered above average.

While it was a small sample size, Frias did not pitch well in that stretch. His command was sub-par, rendering his 96 MPH fastball somewhat useless. On April 17, one day after his blowup outing, he landed on the 15-day Injured List with right shoulder inflammation.

Once recovered, Arizona optioned the reliever to Triple-A Reno. His first month with the Aces was disastrous, as he pitched to a 7.94 ERA in the hitter-friendly PCL. But July was a complete 180, as he threw to a 2.53 ERA over nine games, allowing three total runs while striking out 11.

Despite that good stretch, the D-backs designated him for assignment on August 8. Two days later, he was claimed off waivers by the Toronto Blue Jays, and sent to their Triple-A affiliate, the Buffalo Bisons. He made eight appearances with for the Buffalos, allowing only a single unearned run.

On September 6, he was called up by the Blue Jays. Unfortunately, it was an immediate disaster. His first outing with Toronto saw him surrender five hits and four earned runs while only recording one out.

He made three more appearances before being sent back to Triple-A. The righty gave up eight earned runs over 3.1 innings for the Blue Jays.

Ultimately, it was a disappointing regression for the 26-year-old righty. While his velocity and stuff has high potential, he wasn’t able to put it together with his command, and his numbers were poor across the board.

2025 Contract Status: Pre-arbitration, $760,000 with Blue Jays if on MLB roster

There should be little chance the D-backs consider a return for Frias. The young righty has struggled for the most part in his developmental period with Arizona, and seems to be struggling even harder with Toronto.

There remains plenty of raw potential, and the Blue Jays could very well see him turn into a serviceable reliever, but his time with the D-backs’ organization is likely done, at least for the foreseeable future.