The personnel hasn't changed, but Auburn's run game has certainly looked unfamiliar through three games this season.

During Gus Malzahn's tenure at Auburn, a dominant rushing attack has been a staple of the Tigers' offense, but so far this season the run game hasn't been up to Malzahn's standard. The team rushed for just 146 yards on 43 carries -- 3.4 yards per carry -- against FCS program Mercer last weekend, which was the same total the Bears allowed to Jacksonville University two weeks prior, and afterward Malzahn demanded improvement up front.

"That's my biggest concern right now," Malzahn said of the run game. "We've got to be able to run the football better. Obviously, Clemson has a great defense and they shut us down in the run game, but last week we didn't execute like we need to. We've got to do a better job of executing in the run game because you get in league play, you're going to have to run the football effectively to win consistently. Our coaches understand that, and that's been a big point of emphasis."

After an impressive rushing performance in the opener against Georgia Southern, when Auburn totaled 351 yards on the ground while averaging 6.62 yards per carry and getting dueling 136-yard performances from Kerryon Johnson and Kam Martin. After the opener, Auburn was 10th nationally in rushing offense. Since then, however, the Tigers have seen a steep decline in their production on the ground.

Auburn ran for 38 yards on 42 carries against Clemson on Sept. 9 in what was the second-lowest rushing total of Malzahn's career. That dropped Auburn to 52nd nationally in rushing. Then came last week's grind-it-out effort against Mercer, which dropped Auburn to 62nd nationally in rushing yards per game and 89th nationally in yards per carry (3.88).

"Just execution up front," offensive coordinator Chip Lindsey said. "Two weeks ago (against Clemson), a lot of it was personnel. I think this week was just execution. We threw it probably more, too, than has been done and that took away some of the carries."

Auburn finished in the top-17 nationally in yards per carry during three of Malzahn's first four seasons. In 2015, the Tigers finished 70th with 4.35 yards per attempt. The team hasn't finished lower than 35th nationally in rushing yards per game, and it led the nation in rushing during Malzahn's first season.

While Auburn's offensive line has been a sore spot so far this season, Malzahn wasn't prepared to place blame solely on that unit for the team's struggles in the run game.

"I'm going to just say it's an overall execution of everything," Malzahn said. "But you know we weren't able to run the football effective enough Saturday playing the opponent that we were playing."

A common factor during the run game struggles the last two weeks has been the fact that Auburn has relied exclusively on running back Kamryn Pettway. Johnson has been sidelined the last two weeks with a right hamstring injury he sustained in the opener, while Martin has not recorded a carry since his 136-yard effort against Georgia Southern, and Malik Miller has been absent from the backfield altogether the last two games.

As a result, Pettway has shouldered the load. The SEC's leading rusher in yards per game a year ago has carried the ball 56 times for 202 yards and three touchdowns the last two games after being suspended for the opener.

"Obviously, we've got to take care of our guys, but like I said, as that game unfolded it was a close game and a game we should have won and we should have won by more, so I think that had a lot to do with it," Malzahn said when asked if he had concerns about Pettway's durability.

The reliance solely on Pettway has also been somewhat of a limiting factor in the sense that Auburn has not called many perimeter runs the last two weeks, with Pettway being more of a between-the-tackles running back. According to Lindsey, Auburn has instead used swing passes, screens and tosses as a means of getting the ball to the outside, with Lindsey saying that is "kind of our perimeter stuff right now."

Lindsey added that Auburn will "keep an eye on" other opportunities to use a more traditional outside run game moving forward. Those are likely to be presented this weekend against Missouri's 92nd-ranked rushing defense, especially with Johnson's imminent return to the backfield, which will mark the first time this season both he and Pettway will be available for Auburn.

"Now, KJ (Kerryon Johnson) will be back this week, so that will definitely help," Malzahn said. "But Kam Martin is a guy that we know can go in there and do some things and Malik Miller is a guy that we've got a lot of trust in, too."