Bill Polian breaks down some of the shortcomings Bengals RB Joe Mixon has shown so far at the professional level. (1:01)

Cincinnati Bengals coach Marvin Lewis, responding to Joe Mixon's comments about not getting any second-half carries against the Pittsburgh Steelers, said the rookie running back needs to grow up.

"You should show maturity just like everybody else. Everybody wants to be out there all the time," Lewis told reporters Monday, according to the team's website. "But we're not going to create a run when we are down by 12 or 15 [points]. We're not going to create it."

Lewis pointed out that the Bengals did throw two second-half passes to Mixon on Sunday, and one turned into a fumble (which the Bengals recovered).

"I saw a ball go on the ground when he received two balls thrown to him, which are the same situation. We got to handle it all the time the correct way, and be strong enough to not be led into questions after the game, which unfortunately he doesn't know enough about," Lewis said.

After the Bengals' 29-14 loss in Pittsburgh, Mixon complained about his lack of touches, pointing out that the Steelers' Le'Veon Bell got 35 carries while Mixon had only seven, all in the first half. He finished with 48 yards rushing and three receptions for 20 yards.

Joe Mixon had seven carries for 48 yards in the Bengals' loss to the Steelers on Sunday. Joe Sargent/Getty Images

Whereas Lewis was dismissive of Mixon's frustration, offensive coordinator Bill Lazor said Monday he understood why the rookie was upset.

The Bengals only had 19 yards of offense in the second half, and two drives ended in turnovers. Lazor broke down why Mixon didn't have a second-half carry and why the Bengals stopped running the ball.

"There were a couple reasons, I think. If you look at how those series went, first of all, we were three-and-out, interception, interception, three-and-out," he said. "So when you have a 51-play game, no one gets it enough. And there were a couple plays we chose to put someone else in for particular things and it had nothing to do with Joe; it worked out that way."

Lazor said that even when the Bengals win, some skill players are unhappy with the number of touches they receive.

"Not everyone is going to be happy with their touches all the time. And I've done it before, so I understand. Some guys handle it better than others, some of them it shows by the look on their face, some of them by their body language, you can tell. It's not the first time," he said.

ESPN's Katherine Terrell contributed to this report.