Arizona Diamondbacks’ bullpen vital in sweep of Pirates

It turns out sending pitcher Matt Koch down to Triple-A Reno for an extra bullpen arm was a well-conceived plan.

After Clay Buchholz exited the game Sunday with tightness in his left side, the Arizona Diamondbacks were forced to rely on their bullpen for the second time in the last three games.

Not to worry. The D-backs bullpen doesn’t have the best ERA in the MLB for nothing.

Andrew Chafin entered the game in the sixth inning and struck out four of the six Pirates batters he faced. He threw 29 pitches over 1.2 innings.

Yoshihisa Hirano closed out the seventh inning and then pitched the next. He only need 15 pitches to extend his scoreless streak to 22 games.

Then, Brad Boxberger took the mound for the ninth.

His 10-pitch, seven-strike outing seems to be an indication he’s moved past the blown saves in his last two appearances.

The D-backs defeated Pittsburgh 3-0 and swept the four-game series.

Sunday’s pitching was an extension of a D-backs series that could have imploded early had the pen not been ready to battle.

It’s not unusual to see a bullpen struggle after a game like Friday, a 13-inning affair in which Arizona needed six relievers.

Hirano, Archie Bradley, Fernando Salas, Chafin and McFarland combined to throw five scoreless frames. Boxberger allowed an unearned run before getting out of a bases-loaded, one-out jam.

But depth allowed the D-backs to get through the weekend unscathed.

Jake Barrett, who was called up in place of Koch, closed out the ninth inning in Arizona’s 9-3 win Thursday and then threw a meaningless ninth inning on Saturday.

Though he allowed a run, it saved an arm for Sunday.

With the exception of Braden Shipley, who was called up Sunday morning in place of Barrett, every arm in the bullpen got a go at the Pirates.

The eight pitchers allowed only three runs – two unearned – through 16 innings. Its series ERA of 1.69 lowered an already-league leading bullpen ERA.

With the sweep, Arizona extended its National League West lead over the Los Angeles Dodgers to three games.

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