RENTON, Wash. -- Seattle Seahawks running back Thomas Rawls said recently that he becomes a different person when he puts his helmet on.

"I turn into T. Rawls, man," he said. "I think I've got an alter ego when I'm out here sometimes. I don't know man. I'm just out here having so much fun. ... I try to bring it every day, and hopefully somebody can pick up on it because that aggression and that mentality can take you a long way."

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Rawls' energy has been evident to anyone paying attention this summer. The third-year running back has been bouncing around the practice fields in between reps. When he touches the ball, he's looking to punish defenders. It's the same mentality that made Rawls so successful as a rookie, when he ran for 830 yards and averaged a league-best 5.6 YPC.

When the Seahawks signed Eddie Lacy as a free agent this offseason, it seemed reasonable to conclude that they expected him to be the feature back. But Rawls has been running with the first team. During the first preseason game Sunday night against the Los Angeles Chargers, Rawls was the starter, and Lacy came in with the second unit.

Last year, the first one in the post-Marshawn Lynch era, 18 different Seahawks carried the football. Pete Carroll doesn't want a repeat of that in 2017, but with the opener three weeks away, how Seattle plans to divide up carries remains unclear.

Lacy has passed all of his weight checks, per Carroll. He hasn't had a lot of highlights in camp, but that may be more because of his style than anything else. Lacy's a big, physical runner who has shown on film that he can pick up yards after contact. And there's just not that much contact in practice. Lacy ran four times for 10 yards in the preseason opener.

Rawls carried twice for 5 yards on Sunday and still has plenty to prove. He averaged 3.20 YPC last season, which ranked 40th out of 42 players.

Rookie Chris Carson continues to be a name to watch. He ran seven times for 19 yards and two touchdowns against the Chargers but was more impressive than those numbers indicate.

"He had a run taken away from him by a penalty that would've given him some good numbers, but he ran effectively with a nice style down by the red zone and going in with two good goal line runs," Carroll said.

Carson is clearly ahead of Alex Collins and continues to climb up the depth chart. When Rawls got the day off Tuesday, Lacy, Carson and C.J. Prosise all got turns with the first team. Prosise is expected to handle the bulk of third-down duties -- at a minimum.

The Seahawks' offseason was built largely on recommitting to the run game. They finished 22nd in rushing efficiency last year after ranking in the top seven during the first four years of Russell Wilson's career.

Having a healthy Wilson will lead to better results. But the Seahawks will need to use the rest of the preseason to determine roles for what suddenly looks like a deep group of running backs.