BALTIMORE -- Chris Davis didn't look like the majors' hottest hitter. Until it mattered.

The Orioles' first baseman became the fourth player in major-league history to hit a home run in each of the first four games of a season, and this was his biggest yet. With the bases loaded and the Twins clinging to a 5-4 lead, Davis smacked Tyler Robertson's first pitch, an 86-mph fastball, several rows deep into the left-field bleachers for his second career grand slam. With that one swing, Davis increased his RBI total to 16 just four games in, and handed Minnesota a 9-5 loss.

Liam Hendriks allowed four runs over 4 2/3 innings for the Twins in his 2013 debut, the first Twins starter to fail to pitch into the sixth inning this year. But the Twins scored five runs off Baltimore starter Jake Arrieta and led until Davis' grand slam delighted the sellout Opening Day crowd at Camden Yards.

The Twins got four of their runs in the fourth inning, all of them with two outs, by stringing together four hits and a walk to overcome the Orioles' early 1-0 lead. Chris Parmelee's two-out single up the middle brought home one run, Brian Dozier followed with a two-run triple, and Eduardo Escobar added an RBI single. And Dozier broke a 4-4 tie in the sixth inning with a sharp single up the middle off reliever Troy Patton.

But Casey Fien and Robertson gave it back in the eighth inning. With setup man Jared Burton unavailable because he had pitched each of the past two days, Fien allowed the tying run on a bases-loaded single by Adam Jones. The Twins turned to Robertson to face Chris Davis, who homered in each game of the Orioles' series in Tampa Bay this week. Davis had a single and a sacrifice fly in four previous plate appearances, but this at-bat wasn't nearly so quiet. He timed Robertson's first pitch perfectly, sailing the ball to the opposite field, far over Josh Willingham's head and into the left-field stands.