BOSTON -- Offense hasn't been a problem for the Red Sox through 81 games, but Boston's struggles on the mound are threatening to undo all the good the team is doing at the plate.

At the midway point, the Red Sox (44-37) have scored a league-leading 451 runs, a total they added to handsomely Sunday in a 10-5 win over the Los Angeles Angels.

However, their mediocre pitching -- a 4.49 team ERA that ranks 11th in the AL -- might prove troublesome entering their three-game series with the Texas Rangers that starts Monday.

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"While this is a strong offensive team, we still have areas of improvement," Red Sox manager John Farrell said. "The key (to the second half of our season) without a doubt will be to stabilize our pitching, particularly in the rotation."

The Rangers (52-31) own the top record in the AL, although they are in the midst of a little funk after dropping two of three games -- including a 5-4 defeat Sunday -- to the major-league-worst Minnesota Twins.

Overall, the Rangers have lost four of their past five.

"We hit some balls hard today," Texas manager Jeff Banister said after his team's eight-hit attack Sunday. "We hit them right at some people, and we hit some line drives into the outfield. Couple feet either way, and it's a different ballgame."

As a unit, the Rangers' offense has held its own, scoring 407 runs, a total that is tied for seventh in the majors.

On Monday, Texas will have to contend with one of Boston's most consistent arms, right-hander Rick Porcello (9-2, 3.78 ERA).

Porcello has pitched well at home this season, going 6-0 with a 3.48 ERA in seven starts at Fenway Park this year.

His numbers against Texas haven't been as encouraging, though. In eight career starts against the Rangers, Porcello is 4-4 with a 5.86 ERA.

Shin-Soo Choo, who hit a solo home run and drove in three runs total Sunday, has hit Porcello well historically, batting .286 (10-for-35) with four RBIs against him.

Adrian Beltre is 8-for-21 with a solo home run off Porcello.

Last time out, Porcello allowed a run on five hits and three walks while striking out eight in a six-inning, 8-2 victory at Tampa Bay on Tuesday.

Nick Martinez (1-1, 5.00 ERA) has the task of containing the Red Sox's high-powered offense in Monday's opener.

The right-hander will be making his fourth start for the Rangers after giving up two runs on three hits and five walks with two strikeouts in a five-inning no-decision Wednesday at the New York Yankees.

Martinez is 0-1 with a 4.15 ERA in two career starts against Boston, including a June 24 start in which he allowed four runs on six hits over six innings in another no-decision.

Mookie Betts is 3-for-7 against him, while Jackie Bradley Jr. is 1-for-3 with a two-run homer. Hanley Ramirez has also teed off on Martinez, going 3-for-5 with two home runs and three RBIs.

Texas took two of three games against Boston when the teams met for a weekend series in Arlington on June 24-26. The Rangers won five of seven meetings with the Red Sox last season.