HOUSTON -- Atlanta Falcons offensive coordinator Kyle Shanahan will become the next head coach of the San Francisco 49ers once a contract is placed in front of him, a source told ESPN.com following the Falcons' 34-28 loss to the New England Patriots in Super Bowl LI.

Shanahan was not able to accept a contract offer from the 49ers until after the Falcons' postseason run concluded. He interviewed with the 49ers twice during the postseason and had a conversation with newly named 49ers general manager John Lynch, who called Shanahan and volunteered for the job without any previous front-office experience. Shanahan, 37, is expected to sign a six-year deal to run concurrent with Lynch's contract.

In two seasons with the Falcons, Shanahan helped transform quarterback Matt Ryan into the league MVP. He was the playcaller behind the NFL's top scoring offense in 2016, as the Falcons averaged 33.8 points per game.

But Shanahan will leave Atlanta with criticism following him. He answered questions about not running the ball in the latter stages of the Super Bowl. One was a third-and-1 pass play with 8:31 left in the fourth quarter and the Falcons leading 28-12. Ryan was sacked by Donta Hightower on the play and lost the ball, which was recovered by Alan Branch. The Patriots grabbed the momentum with a touchdown and two-point conversion immediately after the turnover, closing the gap to 28-20.

Kyle Shanahan, who faced criticism for not running the ball in the latter stages of the Super Bowl to push the Falcons into field goal range, said after the game that "we tried our best to get back in but couldn't get it done." Jason Getz/USA TODAY Sports

On the next drive, Ryan again was sacked on a second-and-11 run play from the Patriots' 23-yard line. That set up a third-and-23 play from the 35, and then a holding call on left tackle Jake Matthews pushed the Falcons out of field goal range.

"The thought is to get as many yards as you can,'' Shanahan said of not running while in field goal range. "And we were right there on the fringe. It was by no means an easy field goal. From what I remember, we ran in on first-and-10 and lost yards. Got into second-and-11, so we try to get a pass to get us back into a manageable third down, closer to the field goal, and we took a sack. Taking a sack ... got us into a third-and-20, so we threw a quick pass trying to get back into field goal range, which we did. But there was a holding call on the play. And when you get a holding call on third-and-20, it goes back that far. We were way out of field goal range. We tried our best to get back in but couldn't get it done.''

Shanahan was then asked about the fine line between being aggressive with the pass and being mindful of clock management.

"It's not really the run-pass ratio that I look at,'' Shanahan said. "It's you stay on the field, and you run your offense. When went three-and-out two times, which was huge. I think we had second-and-1 on both of those. To not convert on second-and-1 and then third, it was tough. That's why we let them get back into the game.''

It's unclear how the Falcons plan to address the offensive coordinator position once Shanahan officially leaves. The Falcons also are likely to lose quarterback coach Matt LaFleur, who is expected to be interviewed by the Los Angeles Rams. Offensive line coach Chris Morgan said it's only natural to want to take the next step and become an offensive coordinator. Wide receivers coach Raheem Morris believed he was capable of calling plays on offense or defense when he was the head coach at Tampa Bay.

Falcons coach Dan Quinn said last week that the offensive system is "100 percent'' in place, which would indicate that he wants to keep Shanahan's scheme even if Shanahan is not around.

Asked if he could confirm that Shanahan was set to leave the Falcons, Quinn said simply, "It's not my story to tell.''