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Oakland A’s prospect watch: Edwin Diaz finding his bat in Single-A Beloit

Edwin Diaz
Justin Nuoffer Photography | Beloit Snappers

The Single-A Beloit Snappers haven’t come close to a winning record since 2013, but their offense had them off to a 28-26 start this year heading into Sunday. Within the 16-team Midwest League, they rank third in OPS, and fifth in runs per game as well as homers. They’ve been especially hot over the last two weeks, averaging over six runs per game.

One key part of that success has been Edwin Diaz. The infielder was not anywhere on our prospect radar during the offseason, but entering Sunday’s doubleheader he carried a 12-game hitting streak and his 145 wRC+ led the Snappers. The right-hander’s overall profile suggests multiple encouraging strengths:

Diaz, 2017: .294/.380/.483, 145 wRC+, 6 HR, 12.0% BB, 25.9% Ks

I’m not sold that he can keep his batting average that high unless he can eliminate some of the swing-and-miss from his game, but either way he’s showing he can get on base and contribute some power. (Video link: Home run) Considering that he’s split his career between SS and 3B (as opposed to, say, LF and 1B), these are the early signs of a new name to really start watching.

And who is Diaz? Perhaps “new name” isn’t entirely accurate, because he’s quietly been in the organization for a while. The A’s drafted him in 2013, in the 15th round out of high school in Puerto Rico. This is his third season in Beloit, and at age 21 he’s finally putting together a breakout performance. Context: If he’d gone to college then this would be his senior year, so age-wise he could just as easily have been part of the 2016 draft class. He’s still one of the youngest players on the Snappers’ roster.

There’s always room for one more sleeper on the radar, and Diaz is well on his way to that status. He appears to bring multiple skills to the table, and he’s shown significant improvement each year while never being too old for his league. Let’s see what June brings!

Extra note: Diaz missed a couple games this week despite his recent red-hot stretch, but Garett Mansfield of Snappers media relations reports it was just an “illness going around the team.” Indeed, Diaz was back in the lineup in Sunday’s opener, though he snapped his hitting streak in his return.

The other sluggers

At the beginning of the season, we identified a group of four sluggers who were racking up whiffs even faster than they blasted dingers. Over time, Diaz has set himself apart from the rest, both in terms of having the most success but also in the sense that he’s moved away from that all-or-nothing profile. Here’s a look at the progress of the others.

Numbers don’t include Sunday’s games.

Name Pos Avg/OBP/SLG HR BB% K% SwStr% wRC+
Edwin Diaz IF .294/.380/.483 6 12.0% 25.9% 11.9% 145
Collin Theroux C .223/.320/.509 9 12.5% 42.2% 17.8% 133
Miguel Mercedes 1B .232/.285/.470 11 5.5% 26.5% 15.7% 111
JaVon Shelby OF .244/.333/.381 5 10.4% 35.8% 14.7% 106

A few notes:

  • Theroux over his last five games: 6-for-19, 4 HR, 9 Ks, 1 BB. You can’t get much more all-or-nothing than that.
  • Mercedes, meanwhile, is having a different level of success. Specifically, he’s keeping his power while cutting down on the Ks. Over his last 13 games (including Sunday’s opener), he’s batting .326 with more extra-base hits (7 XBH, including 4 HR) than strikeouts (6 Ks, in 49 PAs). If he keeps making that much contact then you might just see him in the headline of our next Beloit update.
  • Shelby has seen his power taper off after an early-season surge, but keep in mind that he’s also learning to play the outfield after being drafted as a 3B. Furthermore, he’s now splitting time between CF and RF, so he’s actually picking up two new positions on the fly. His batting line is discouraging right now outside of his walk rate, but he deserves a healthy dose of patience.

Mondou keeps setting table

The other set of noteworthy hitters in Beloit is the table-setters. Last time we took a deeper look at this group, and here’s an update on their progress:

Numbers don’t include Sunday’s games.

Name Pos Avg/OBP/SLG HR BB% K% SwStr% wRC+
Nate Mondou 2B .335/.404/.434 0 10.7% 13.0% 7.2% 138
Luis Barrera OF .318/.358/.450 2 6.0% 18.1% 10.1% 128
Luke Persico OF .292/.360/.433 3 9.5% 14.5% 8.5% 126


  • Mondou recently enjoyed a stretch in which he recorded multiple hits in six out of seven games. Dude just keeps on hitting, and with a batted ball profile full of contact and liners and using the whole field. But will his lack of power become a problem as he moves up the ladder?
  • Barrera hit .333 in May, with a bunch of extra-base hits and even a handful of walks. The 21-year-old wasn’t that far from cracking our Community Prospect List last winter.
  • Infielder Eric Marinez just misses my cutoff for now. His line is buoyed by a strong walk rate, but he’s not bringing anything else to the table yet — meh average, no power, more whiffs than his modest strikeout rate suggests.

Chalmers sent down

Beloit’s pitching staff lost its highest-profile prospect when RHP Dakota Chalmers was reassigned to Low-A Vermont. I don’t know if this move was pre-planned, with the 20-year-old logging some time in Single-A before the short-season Lake Monsters begin their campaign, or if it’s the result of his shaky performance: 4.34 ERA, 29 ip, 47 Ks, 29 BB. Yowza, a walk per inning.

Either way, Chalmers is still quite early in his development and has plenty of time to continue refining and commanding his powerful stuff. It just won’t continue in Beloit for the time being. Here are the top remaining names:

Numbers don’t include Sunday’s games.

Brendan Butler 2.32 54⅓ 64 13 1 2.54
Brandon Bailey 2.31 35 42 8 2 2.70
Dalton Sawyer 2.16 50 58 19 3 3.16
Ty Damron 5.11 37 40 16 1 3.31
Matt Milburn 5.77 43⅔ 40 13 3 3.66


  • Bailey now leads the team in swinging strike rate (17.0%), and in his last two outings he’s fanned 12 batters over seven innings.
  • Milburn and Damron are both close to slipping off the radar, though strong peripherals are keeping them on for now. Between the two, Milburn has the edge in whiff rate, walk rate, and grounders, while Damron has the advantage of being a lefty.
  • Zack Erwin is back! The lefty, acquired in the Brett Lawrie dump, was a flop last year in High-A Stockton and then got hurt. Now he’s back, and in two outings he’s tossed seven scoreless frames (6 Ks, 2 BB).
  • The top reliever right now is RHP Sam Sheehan, last year’s 31st-round pick. His line: 2.45 ERA, 11 ip, 15 Ks, 5 BB, 1 HR, 3.59 FIP, 63.6% groundball rate.

Sunday’s games

A full slate, plus a couple makeups!

Triple-A Nashville: Won 6-0, Paul Blackburn vs. Iowa
Double-A Midland (resumed): Lost 9-5, Ben Bracewell vs. NW Arkansas
Double-A Midland: LIVE, Grant Holmes vs. NW Arkansas
High-A Stockton: 2:15 p.m., Angel Duno vs. Lake Elsinore
Single-A Beloit (resumed): Won 4-3, Brandon Bailey vs. Wisconsin
Single-A Beloit: 2:35 p.m., Dalton Sawyer vs. Wisconsin

The Snappers game was suspended after three innings last night, and they needed 10 more frames to wrap up the victory in the 13th. Now they get to play another! Also, to update the intro paragraph of this article, they are now 29-26 for the season.

In Nasvhille, Blackburn threw seven scoreless innings, allowing only two hits and a walk on 83 pitches. In Midland, Grant Holmes struck out nine batters in six frames, and Tyler Marincov homered in both games.

Link to box scores