Series preview: Arizona Diamondbacks bring surprisingly strong hitters, surprisingly weak starting pitchers to PNC

The Pirates kick off a three-game series against Arizona at PNC Park tonight. Here's what to expect from the Diamondbacks, besides uniforms and trades that are equally strange.

Game times and probables

Today, 7:05: Shelby Miller vs. Francisco Liriano
Wednesday, 7:05: Rubby De La Rosa vs. Jeff Locke
Thursday, 12:35: Patrick Corbin vs. Gerrit Cole

The Diamondbacks made big moves last winter to upgrade their rotation, nabbing Zack Greinke and Shelby Miller in high-profile moves designed to force their way into contention. The team's rotation has been a pronounced weakness so far, however, which is the main reason the Diamondbacks are 21-25 despite having dealt a ton of minor-league talent in an effort to win now.

The biggest culprit has been Miller, acquired from the Braves last December in a ludicrous trade. He currently has a 6.64 ERA and nearly as many walks (25) as strikeouts (27) in 40.2 innings. His fastball has been significantly less effective than it was in the past, probably in part because his velocity has dropped into the 92-94 MPH range. (That velocity drop actually began in the middle of last season, before the trade.)

Rubby De La Rosa is trending in the opposite direction. Now 27, he's in the midst of his best season so far, with a 9.4 K/9 that finally matches his mid-90s heat and plus slider. His ground ball rate is also up a bit, to a very healthy 52.6 percent. It's harder to get a clear read on Patrick Corbin, who's in his first full season back from Tommy John surgery, but he's been reasonably effective thus far, with a 3.99 ERA, 6.2 K/9 and 2.7 BB/9.

Position players

C Welington Castillo, Chris Herrmann
1B Paul Goldschmidt
2B Jean Segura
SS Nick Ahmed
3B Jake Lamb
IF Phil Gosselin
LF Yasmany Tomas
CF Chris Owings
RF Brandon Drury
OF Michael Bourn
OF Rickie Weeks

This looks like a ridiculous group -- the outfield, in particular, looks horrible after injuries to A.J. Pollock and David Peralta. (And not just because of Michael Bourn, whose recent signing earned eye-rolls from fans but who actually wasn't a terrible flier for a team in need of a backup.) Diamondbacks position players rank eighth in the majors with 7.5 fWAR, though, and it hasn't even been the brilliant Paul Goldschmidt leading the way. Instead, it's been third baseman Jake Lamb, who's taken a huge step forward in his second full year in the league, batting .272/.353/.517 with almost as many extra-base hits as he had in twice as many plate appearances last year.

Jean Segura, too, has hit well after two miserable years in Milwaukee (after which he came to Arizona in another trade that initially looked dubious, but that now looks significantly better). Also, Welington Castillo and Chris Herrmann have been baseball's best catcher tandem so far. That won't last, but the duo does have real power, with 12 home runs between them.

The D'backs have been very tough against left-handed pitching this season -- their .833 OPS against lefties ranks third in the majors. Look out for Goldschmidt, Castillo, Segura, Yasmany Tomas and Chris Owings against Francisco Liriano and Jeff Locke.

Bullpen

Brad Ziegler
Tyler Clippard
Daniel Hudson
Randall Delgado
Andrew Chafin
Zac Curtis
Jake Barrett
Evan Marshall

The Diamondbacks have already used 16 relief pitchers so far this season, which might ordinarily be the sign of a terrible bullpen, but the Diamondbacks' bullpen isn't awful -- Tyler Clippard, Daniel Hudson and hard-throwing rookie Jake Barrett have all provided good innings so far.

Watch for Brad Ziegler, though. He's always been highly unconventional, especially for a closer -- he's a submariner who throws mid-80s fastballs, relies heavily on his changeup and never strikes anyone out but still gets good results due to powerful ground-ball tendencies. This year, though, his fastball is softer than ever. His 83.2-MPH average fastball velocity is fourth slowest of any pitcher who's thrown at least 10 innings, ahead of only Jered Weaver and knuckleballers R.A. Dickey and Steven Wright. Ziegler is also walking 4.9 batters per nine innings, and his hard contact rate is the highest of his career. He has a 2.95 ERA so far this season, but that seems unlikely to continue.

Another fun player to watch is Zac Curtis, a lefty the Diamondbacks promoted to the big leagues late last month even though he'd never played above the California League. Adding him to the big-league roster was a highly unusual move, but probably not a silly one -- prior to the promotion, he'd struck out 22 batters in 10.1 innings at Class A+, and he has yet to allow a run in the big leagues.