BOSTON — Rubby De La Rosa pitched seven solid innings and Mike Napoli hit a tiebreaking homer to lift the Boston Red Sox to a 2-1 victory over the Kansas City Royals on Saturday night.

It was the sixth win in seven games for the defending World Series champions, who are looking to climb from the AL East’s basement.

Kansas City’s Eric Hosmer extended his career-best hitting streak to 15 games with a single. The Royals lost for the eighth time in 11 games, falling to 10-20 in one-run games after leading the AL with 31 victories last season.

Napoli’s homer in the sixth cleared a billboard atop the Green Monster seats and completely left the park.

De La Rosa (3-2) had another strong start in Fenway Park, giving up one run on five hits, walking four and striking out two. He worked out of trouble most of his outing.

Danny Duffy (5-10) allowed two runs – one earned – on six hits in 62/3 innings. It was his fifth loss in six starts, but he’s allowed two or fewer runs in four of the losses.

Andrew Miller pitched a perfect eighth and All-Star Koji Uehara a 1-2-3 ninth for his 20th save in 22 chances.

In two of his three home starts, De La Rosa has pitched seven shutout innings. In his last one, he gave up three runs in five innings.

De La Rosa stranded runners at second base in four of the first six innings, twice also leaving a runner on first.

The Royals grabbed a 1-0 lead in the third when Jarrod Dyson tripled and scored on shortstop Omar Infante’s sacrifice fly.

Infante’s fielding error allowed Boston’s tying run in the fourth. With runners on first and second, Infante had Shane Victorino’s an inning-ending, double-play grounder go right through his legs, scoring Napoli.