A four-run first inning and Nick Pivetta's seven scoreless frames led the Boston Red Sox to a 5-3 win over the host Pittsburgh Pirates on Tuesday.

Tommy Pham went 2-for-4 with two runs from the top of the lineup to pace the Red Sox in their second straight win and fourth in five games.

Pivetta (9-9) allowed just one hit and three walks, striking out six. The righty got out of a two-out jam in the first inning after Bryan Reynolds walked and Ben Gamel singled before ultimately cruising to his first win since June 24.

Gamel went 2-for-4 and drove in all three Pittsburgh runs on a two-out, bases-clearing double in the eighth inning.

Matt Barnes struck out two in a 1-2-3 ninth to log his third save of the season, sending Pittsburgh to its fifth straight loss and ninth in 11 games.

Pirates starter Mitch Keller (4-9) lasted just two innings in his first career outing against Boston, allowing five runs (four earned) on five hits and three walks. Keller was later diagnosed with right shoulder fatigue.

Chase De Jong held the Red Sox hitless over the following four innings, allowing only a leadoff walk to Eric Hosmer in the sixth.

Boston sent six batters to the plate before an out was recorded and followed its four-run first inning with another marker in the second.

Pham's leadoff single and walks to Rafael Devers and J.D. Martinez immediately loaded the bases before Alex Verdugo grounded a run-scoring single through to right.

Back-to-back RBI singles by Christian Arroyo and Hosmer followed, and Enrique Hernandez made it 4-0 with a sacrifice fly to deep left in his first plate appearance since returning from the injured list (right hip flexor strain) following a 60-game absence.

In the second, Verdugo reached and Pham scored when Reynolds dropped a fly ball in center.

After Pham's one-out single in the second, neither team had a hit until Pirates catcher Jason Delay lined a hit off Red Sox reliever Austin Davis with one out in the eighth. Tucupita Marcano then walked and Kevin Newman singled to load the bases, which Gamel cleared on one swing against John Schreiber.

--Field Level Media