The Tampa Bay Rays returned home with the AL East lead.
The Arizona Diamondbacks are trying to climb back into the top spot in the NL West.
The surging Rays open their second-half home schedule Tuesday against the Diamondbacks trying to tie their franchise record for wins in a single month.
Tampa Bay (63-43) made the most of its chance to grab the division lead Monday, beating Boston 2-1 in a makeup game from Thursday for its fourth win in five games. The Rays have set a club mark with 20 wins in July and have two chances to match the team record set in August 2008 with a 21-7 mark.
After trailing the Red Sox by 2 1/2 games at the All-Star break, they have won 22 of 26 to overtake them by one-half game. Rays starters improved to 18-3 with a 2.17 ERA during that run after David Price threw 7 1-3 innings of one-run ball Monday.
However, Tuesday's pitcher Roberto Hernandez (5-11, 4.92 ERA) has yielded at least three runs in each of his last nine outings.
The right-hander, tied with Toronto's R.A. Dickey for the second-most losses in the AL, could be on his way to the bullpen with Joe Maddon contemplating using a four-man rotation of Price, Chris Archer, Matt Moore and Jeremy Hellickson starting later this week.
Hernandez, though, can't shoulder all the blame for his recent struggles. His run-support average is a team-worst 2.89 since June 16, and he's 2-6 with a 4.98 ERA in that stretch.
"I think that's called bad luck," catcher Jose Molina told the Rays' official website after Hernandez gave up three runs in five innings in last Tuesday's 6-2 loss at Boston."... It's a shame that we can't perform the way we know we're capable of when he's pitching. That's pretty much wasting an outing for that pitcher."
The Diamondbacks (54-51) did that Sunday, finishing with three hits and going 0 for 5 with runners scoring position to waste eight strong innings from Patrick Corbin in a 1-0 loss to San Diego.
Arizona has dropped 2 1/2 games behind the Los Angeles Dodgers for the West lead after heading into the break leading by that margin.
"We haven't played our best baseball, we know that," Corbin told the Diamondbacks' official website. "I don't know why, but we're trying to figure it out. Hopefully, we can go over there and get some wins."
The Diamondbacks, though, open a stretch of 18 of 21 against teams with winning records.
They'll open their six-game trip with Kennedy (3-7, 5.22) getting his 10th chance to record win No. 50. The right-hander, riding the longest winless stretch of his career, avoided a fifth consecutive loss Wednesday when Arizona rallied from six down before falling 7-6 in 12 innings to the Chicago Cubs.
"It's all about pitch execution," manager Kirk Gibson said. "He started out pretty good, but then he made some mistakes - they hammered them."
Rays rookie Wil Myers has been doing that to opposing pitchers, batting .463 with four homers and 12 RBIs in a 10-game hitting streak.
Jason Kubel, who was scratched Sunday with a sore back, has faced Hernandez more than any other Diamondback, going 14 for 38 (.368) with three homers and three doubles.