Yoan Lopez

Lopez throws in the mid-to-upper 90s with a sharp slider. Years ago, that would have been an attractive recipe to follow to see if he could close. Nowadays, those are the characteristics of most relievers in baseball. They all throw hard, and they all have some sort of breaking pitch. Despite that 1-2 punch, Lopez had a 17.1 K% last year and allowed 1.6 homers per nine innings. When a guy with that stuff has trouble missing bats and barrels, that speaks to the low life on the fastball. He has top 10th percentile velocity on his fastball, but bottom third percentile on its spin. He throw the pitch 60% of the time, so when he misses spots, it gets punished. He had the worst exit velocity off his batted balls in the league last year. Something has to change, or he will move to another league in a hurry.

Lopez was called up from Double-A Jackson in September for his big-league debut and allowed three runs in nine innings of relief while posting an impressive 11:1 K:BB. The lack of walks in his short major-league sample were a pleasant surprise, as he'd walked 10.3% of batters at Jackson. It's unclear if Lopez will make the Opening Day roster, but he appears to be big-league ready and could work his way into a high-leverage role if given the chance. Whether or not he can keep avoiding walks will likely determine whether he spends most of his time in the sixth inning or the eighth. Archie Bradley is the favorite for the ninth inning heading into the year, but Lopez could be a dark horse should Bradley take a step back or get injured.

Arizona forked over an $8.27 million signing bonus before the 2015 season to nab Lopez —a record bonus for an international amateur. However, Lopez’s debut season was a disappointment. Injuries limited him to just 48 innings with Double-A Mobile, where he went 1-6 with a 5.06 ERA and 32 strikeouts. Lopez also missed a team bus and went AWOL for a few days in July, which raised concerns about his makeup. He can hit the mid-90s with his fastball, and he also mixes in a slider and changeup. But like with many young pitchers, control is still an issue for Lopez, evidenced by his 4.5 BB/9 in 2015. The potential for a mid-rotation arm is certainly there, based on his physical traits. However, his control and makeup concerns could lead to him being a reliever long term.

Lopez is a Cuba defector who had a 3.12 ERA with a 28:11 K:BB ratio in 49 innings in 2013-14 for Isla de la Juventud in the Serie Nacional, Cuba's top professional league. He hit 100 mph on the radar gun in some workouts for scouts and is seen having a mid-90s fastball. He'll likely sign with a MLB team at some point in 2015 and it may not take long before he's ready for the majors.