23. Jhonathan Diaz
I’m not going to lie, I struggled with this one. I really wanted to put Jhonathan Diaz a lot higher on this list, but couldn’t bump anyone. The left-handed pitcher was intriguing entering the year and only rose his stock more.
Diaz was consistently strong all season for the Full-A Greenville Drive. He posted a 3.00 ERA and 1.06 WHIP in 153 innings for Greenville. In that time, Diaz struck out 147 batters while opponents hit .223 against him.
Those are great numbers, sure – but his last five starts showed off some ridiculous potential. In Diaz’s last five starts, the 22-year-old threw 32 innings and allowed two earned runs. For those trying to do the math, that’s a 0.56 ERA.
His overall numbers were an incredible improvement over 2017 when he spent all year in Full-A and posted a 4.57 ERA and 1.45 WHIP.
Diaz is another pitcher without any truly dominant pitches. That being said, everything he offers is a plus-pitch for the time being and project to be that way in the future as well. This is a positive because it means Diaz has four potential Major League pitches.
At the same time, it could be seen as a negative because there’s no true “out” pitch that he can go to when in trouble. I don’t look at it that way though. Having an over-powering pitch is nice but it doesn’t mean much if it’s your only good pitch. Then teams will start to lock in on it. Having four plus-potential pitches gives Diaz options and keeps hitters on their toes.
This could be my bias towards the pitch talking, but Diaz’s best offering is his changeup.
At the moment he’s probably seen as more of a back-end rotation arm. If Diaz can build off last season’s campaign the projections will improve though. The Red Sox definitely don’t have a shortage of left-handed arms in their minors.