Landon Sims Makes Successful Return to the Mound

Arizona's No. 20 prospect pitched his first innings with the organization after rehabbing from Tommy John surgery.

This article is part of a series counting down the Diamondbacks Top 30 prospects entering the 2024 season. These rankings are determined by Michael McDermott, in conjunction with the Inside the Diamondbacks staff.

Summary: Landon Sims enjoyed a successful run as Mississippi State's closer when the Bulldogs won a National Championship in 2021. Sims was expected to make the jump to the rotation the following year, but lasted only three starts before needing Tommy John surgery. That caused him to fall all the way to Arizona's pick with the 34th overall selection, signing him for a slightly above slot bonus of $2.347 million. Sims returned to a mound in a competitive situation for the first time in June and got his first action in the pros.  

Rank: 20

Age: 23

Height/Weight: 6'2" 227 lbs.

Throws: Right

Tools: Fastball 50, Slider 60, Changeup 40, Command 45, Overall 40

ETA: 2026

What the D-backs are saying about him?

“He’s a player who had a ton of success in college, won a National Championship at Mississippi State. It’s a big fastball that misses bats, a plus slider, and he has a chance to be a starter.” - Scouting Director Ian Rebhan, 2022

2023 Season Recap: Sims took the mound for the first time since March 2022, pitching first in the complex for a handful of games before finishing the year with Visalia. The D-backs had him on a strict workload, as he amassed only 28 innings between the two levels. His pre-surgery velocity has still not returned, sitting 90-94 MPH after previously operating at 94-98 in college. The fastball played above it's timed velocity, as the carry on the pitch still generated swings-and-misses with a 27% strikeout rate. At the same time the command still hasn't quite returned yet. While the results weren't necessarily great, the success comes in the fact Sims was able to complete his rehab and will have a relatively normal offseason entering the 2024 season.

2024 Expectations: The main key for Sims is showing that he's healthy as he gets further removed from his surgery. That could show up in his velocity and command. The D-backs will still utilize him as a starter in 2024, but there is a short window for him to develop as he'll be Rule 5 eligible following the 2025 season. At the minimum, you'd like to see him work his way up another level to Hillsboro. Additionally if his 2023 velocity is the new normal, From an innings standpoint, his workload should improve from the 28 innings he threw in 2023 to closer to 60-70 in 2024. 

Projection: The projection for Sims is tough if you think he'll return to pre-surgery velocity. That version of him is a Top 10 prospect in the organization, but should his 90-94 velocity be the new normal then his ceiling drops to a bullpen arm. The amount of carry on his 4-seamer will be enough to allow the pitch to play above its measured speed. With the lack of velocity, Sims would need to develop a useable changeup in order to stick as a starter, but if his development goes too slowly a move to the bullpen might be necessary to get him onto the big league roster.

Top 30 Diamondbacks Prospects Entering the 2024 Season