Robert Griffin III has done a better job of protecting himself this season, but there’s still some room for improvement, Redskins Coach Mike Shanahan said.

In Thursday’s 34-27 loss to the Vikings, Griffin was sacked four times and hit eight times. What concerned Shanahan most, though, were two hits he absorbed at the end of runs in the first half.

On the first play, Griffin pulled the ball on a zone read look and gained eight yards to the right, but not before diving awkwardly forward and absorbing a glancing blow from safety Andrew Sandejo. On the other play, Griffin scrambled up the middle for a 12-yard gain. Again, he dived forward—this time in an attempt to cross the goal line—and took a stiff shot to his back from linebacker Chad Greenway.

“I think what you have to do is you have to learn how to slide, and he’s getting better at it, even though [Thursday], I think there [were] a few slides I think he’d like to have back,” Shanahan said. “I don’t think it’s natural for him yet. Head first or if he’s going to be feet first, he’s got to always protect himself.”