BOSTON -- Designated hitter David Ortiz wasn't in the Boston Red Sox's starting lineup for Saturday's 7-6, 11-inning loss to the Milwaukee Brewers, but it was meant to be a planned day off.

With two outs in the bottom of the ninth in a 6-6 game, Ortiz pinch-hit for Jackie Bradley Jr., eliciting perhaps the largest roar of the night, but grounded out to end the inning.

Ortiz had been dealing with a calf strain since spring training. The slugger is now 6-for-18 with a home run and three RBIs through the team's first five games.

Manager John Farrell acknowledged the calf issue before Saturday's game but said it did not factor into his decision-making when he filled out the lineup card.

"I think he deals with a little bit of tightness from time to time. As much as anything, this was more of a planned down day," Farrell said.

Farrell added that he had considered shuffling the lineup after the club had a late arrival from Baltimore on Friday morning before playing a day game hours later, which was preceded by an emotional World Series ring ceremony.

Ortiz's absence was part of a massive lineup shuffle. Center fielder Grady Sizemore led off for the first time, while Daniel Nava dropped from the top spot to bat third, where he had made four prior career starts. In addition, Nava made his first start at first base as regular first basemen Mike Napoli served as the designated hitter.

Mike Carp was originally in the lineup at first base but was scratched due to low back tightness less than an hour before first pitch. Third baseman Will Middlebrooks was subsequently scratched even closer to game time, replaced by Jonathan Herrera. After the game, Farrell said Middlebrooks strained his right calf during pregame sprints Saturday and will receive an MRI on Sunday.

Farrell said as recently as March 27 that Sizemore would not immediately hit leadoff for the Red Sox. The manager noted his desire to have a high on-base percentage individual at the top of the order; Sizemore was one during his best years but Farrell wanted to see how his center fielder would begin the season in that capacity. He was 0-for-4 with a walk and scored a run Saturday.

Earlier, Farrell also hinted at a need to limit Sizemore's workload to a degree, and the extra at-bat a leadoff hitter might get initially was something the team wished to avoid. Sizemore has shown no issues physically as he goes through his first regular game action in over two years.

"Just the way he's responding to games played, the aggressiveness in which he's running the bases, the frequency he's getting on base," Farrell said of Sizemore. "All the above puts him in the spot tonight."

Farrell said before the series began that Sizemore might be a candidate to sit Sunday, a day game after a night game. Nava has gone 2-for-22 with no walks in five games, but Farrell liked the switch hitter in the 3-hole Saturday, when Nava ended up 0-for-5.

"It's also a spot where ideally you're thinking they're going to attack that part of the lineup with a right-handed pitcher, so keeps him on [the left] side of the plate hopefully. He's gained an awful lot of trust in all of us over the year that he's had last year. I think still he's put up a number of good at-bats early on without the batting average to be reflective of it."

Nava hit .322 with an .894 OPS swinging from the left side in 2013.