Nava batted seventh, Podsednik eighth and Shoppach last. The trio won't make anyone forget the home-run power of David Ortiz, Adrian Gonzalez and Kevin Youkilis, but on this day they combined to go 6 for 9 with three homers, four RBIs and four runs.
The victory enabled the Red Sox to finish a grueling stretch of 20 games in 20 days with an 11-9 record, and thrust them back to .500 (22-22). Boston took two of three from the Orioles, who were seeking to win a fourth straight series against the Red Sox for the first time since 1960.
"The top part of the lineup has been doing so much work in 20 days, they were a little under the (weather) today," manager Bobby Valentine said. "The bottom third, (hitting coach) Dave Magadan has done such a fabulous job, we said, 'Let's leave it to those guys to do it.' And they did."
Nava and Shoppach each doubled their home run total for the season; the pair also connected on May 14 against Seattle.
Valentine revealed that the seldom-used Shoppach had griped about his lack of action less than 24 hours earlier.
"Let it be known he came in yesterday and wondered why he wasn't playing. He left angry," Valentine said. "I like him playing when he's angry, I guess."
Acquired from Philadelphia on May 11 and summoned from Triple-A Pawtucket on Tuesday, Podsednik got two hits in his first start with Boston.
"It's good to get back and get my first start, contribute and get a couple runs," he said.
And after that, the Red Sox began looking forward to a well-deserved day off.
"Amazing effort by a group of fabulous professionals who played through a lot of adversity -- time zones, weather, travel," Valentine said. "They did one heck of a job winning the last two series. Going home at .500 is a feather in their cap."
Boston starter Daniel Bard (4-5) allowed two runs, five hits and four walks in 5 1/3 innings.
Johnson's first multihomer game since May 28, 2006, was not enough to prevent the first-place Orioles from losing for the third time in four games. With the potential tying run on second base in the eighth, Johnson ended the inning with a strikeout.
Talking about his homers, Johnson said, "Fastballs. Got some pitches. They were in the middle of the plate and I put some good swings on it."
Regarding the eighth inning, he said, "The last at-bat ... I just couldn't come through."
Arrieta gave up four runs and eight hits in 5 2/3 innings. He's winless in four starts since May 2.
"Well, I think four out of my six innings I allowed the leadoff guy on base," the right-hander said. "When you're pitching with a guy on and no outs to start off an inning, you put yourself in a tight situation."
Baltimore used the speed of leadoff hitter Xavier Avery to take a 1-0 lead in the first. Avery beat out a chopper in front of the plate, went to second on a single by Robert Andino and worked his way home by tagging up on two short fly balls, the last by Chris Davis.
Boston loaded the bases with no outs in the second but scored only one run, on a double-play grounder by Podsednik.
Johnson hit a drive into the right-field seats to start the bottom half, only the third home run allowed by Bard in eight starts this season.
Boston tied it at 2 in the third on a run-scoring double by Will Middlebrooks, but Kevin Youkilis was thrown out trying to score from first base on the two-out hit.
Baltimore went 12-8 over the same 20-game stretch. ... Nava has 11 RBIs in 14 games since joining the Red Sox on May 10. ... Orioles LHP Zach Britton (shoulder) is set to begin his minor league rehabilitation assignment Saturday with Double-A Bowie. ... Baltimore's Adam Jones extended his career-best hitting streak to 15 games. ... RHP Dylan Bundy, the Orioles' top amateur draft pick in 2011, was promoted to Class A Frederick from Class A Delmarva, where he went eight starts without giving up an earned run.