Green Bay Packers running back Eddie Lacy understands why he’s been benched in favor of backup James Starks, but he’s still as perplexed as the rest of the football world as to why he’s struggled so mightily in 2015.

“I honestly don’t know what it is,” Lacy said, via Michael Cohen of the Milwaukee Journal Sentinel. “Definitely, I’m off to a different start. I’m not playing how I was the previous two years. Later on in the season, maybe it’ll pick back up. But as of right now, this is just the move that is going to be.”

Packers head coach Mike McCarthy confirmed Wednesday that Starks would be taking over as the team’s lead back starting Sunday, when Green Bay welcomes the Detroit Lions to Lambeau Field.

Considering the last month of play, it’s not difficult to understand why the Packers are rolling with Starks instead of Lacy, the team’s second-round pick and the NFL’s Offensive Rookie of the Year in 2013.

Starks has played more snaps, received more total touches and been more productive with his opportunities over recent games against the San Diego Chargers, Denver Broncos and Carolina Panthers. While Lacy has dealt with injuries, including an ankle sprain and a groin pull, the difference in quality between the two backs has been obvious.

Even to Lacy.

“This season (Starks) has definitely been the better player between the both of us,” Lacy said. “That’s just the move.”

Lacy strongly denied his ankle was still giving him problems, and he said his weight—a point of contention, both to start his NFL career and now—has had no factor on his play.

But something is definitely wrong. After back-to-back seasons with over 1,100 rushing yards, Lacy is currently on pace for just over 600. He ranks 38h in the NFL in rushing, behind Cam Newton. Through eight games, Lacy currently has more fumbles (three) than touchdowns (two), and his receiving numbers are way down from last season.

The Packers haven’t found many solutions to a problem even Lacy can’t identify. Maybe playing behind Starks for a few games will provide some clarity on one of the NFL’s biggest mysteries of the 2015 season.