B.J. Upton had a grand slam among four hits and James Shields easily outdueled Jon Lester as the Tampa Bay Rays further trimmed Boston’s lead in the wild-card standings Sunday with a 9-1 rout.

Shields (15-10) threw eight strong innings, allowing just a solo homer to Marco Scutaro.

Boston has lost five straight games and nine of its last 11 to see its lead in the wild-card standings cut to just 3 1/2 games over the Rays.

Lester, who had allowed just one earned run in his last four starts, couldn’t make it past the fourth inning. He threw 43 pitches in the first inning alone as Tampa Bay scored three times and cruised the rest of the way.

The Rays, who play a four-game set at Fenway Park later in the week, swept the three-game series to improve to 9-5 against Boston this season.

Lester (15-7) allowed eight hits and three walks as Tampa Bay scored four runs in four innings off the Boston ace.