Red Sox slugger Martinez scratched with back tightness
Boston manager Alex Cora told the media about two hours before the Red Sox were slated to host the Kansas City Royals at Fenway Park.
"It's been acting up, a little bit tight," Cora said. "This morning he felt it, got treatment, so we're going to stay away from him."
The Red Sox enter the game on an eight-game losing streak, their longest since they dropped eight in a row in July of 2015. Their next longest is 10 straight, done in May of 2014.
The defending World Series champions are also 6 ½ games out of a playoff spot and trail the AL East-leading Yankees by 14 ½ games after getting swept in a four-game series over the weekend against their rivals in New York.
With Martinez, the club's usual cleanup hitter out, Christian Vázquez was moved into the DH spot and will bat sixth. Andrew Benintendi was slotted fourth in the order.
Martinez is batting .299 with 24 home runs and 65 RBIs, far off the pace of last season when he put up 43 homers and a major-league leading 130 RBIs.