ARLINGTON — Whatever has been ailing Royals starter Danny Duffy this season, a trip to Globe Life Park, home of the American League’s weakest offense, was at least a temporary cure in an 8-2 win over the Rangers on Thursday night.

In the opener of a four-game series, Duffy allowed one earned run on four hits and two walks in 7 2/3 innings for his longest outing since July 15 of last season, also against the Rangers. He struck out five and threw a season-high 113 pitches, including 76 strikes.

By and large, the 29-year-old lefty has been disappointing this season, posting a league-high six losses entering Thursday with a whopping 6.88 ERA. Until this gem, he had pitched more than six innings just once in 10 starts, and even that was a forgettable performance — a road loss against the Red Sox in which he allowed 10 hits and four homers in 6 2/3 innings.

On Thursday, against a Rangers lineup featuring five players batting under .200, as well as the AL’s worst batting average (.226) and OPS (.685), Duffy was nearly unhittable after Delino DeShields led off the game with a single before being thrown out at second trying to advance on a wild pitch.

Duffy’s fastball was his strikeout pitch as four of his five third strikes came via the heater. But his slider might have been his most effective pitch, as it kept the Rangers hitters off-balance. Duffy said it was as good as it’s been all season.

Royals catcher Salvador Perez paced the offense with four RBIs. Whit Merrifield drove in two runs and last-minute sub Ramon Torres, batting ninth, scored three times.

Having built an 8-0 lead with Duffy well below 100 pitches, Yost sent him back out for the eighth inning, when Rougned Odor broke up the shutout with a single to drive in Joey Gallo, who doubled earlier. Yost and Duffy said there was never any thought of letting the lefty call it a night after seven innings.