SANTA CLARA, Calif. -- On a day when newly minted San Francisco 49ers coach Kyle Shanahan would have preferred to look only to the future, he was asked multiple times to relive the past.

The Niners formally introduced Shanahan and general manager John Lynch to the San Francisco Bay Area media Thursday, and the pair spent about 45 minutes answering questions on a variety of topics. But one subject that came up early and often was the end of Sunday's Super Bowl LI and Shanahan's handling of the playcalling in the second half, as the Atlanta Falcons blew a 25-point lead and ultimately lost to the New England Patriots 34-28 in overtime.

"Obviously, you guys know the result of that, which wasn't easy," said Shanahan, who had been Atlanta's offensive coordinator. "It's as hard as anything I've gone through."

Shanahan has received particular criticism for his handling of a late drive in which Atlanta had moved deep into New England territory with a chance to run the clock down and kick a field goal to make it a two-score game. Hanging on to a 28-20 lead with the ball at the Patriots' 22 and 4:40 to go, Shanahan called for a Devonta Freeman run, which ultimately lost a yard. Instead of continuing to call run plays, Shanahan opted for two passes. The first resulted in a sack and a 12-yard loss; the second resulted in an offensive holding penalty that took away another 10 yards before quarterback Matt Ryan threw incomplete on third down.

Instead of a 40-something-yard field goal attempt that would have made the score 31-20 and burned more time off the clock, Atlanta punted from its 45 and used just over a minute of game clock between Freeman's run and the punt.

"I remember every single play, and I will go over those for the rest of my life," Shanahan said. "That's kind of the life we live as coaches. It's magnified in the Super Bowl, but it's also that case in every game."

After the game, reports surfaced that Shanahan had been heard telling people at the team hotel that he "blew it." Shanahan couldn't recall if that was what he said verbatim but acknowledged Thursday that he understands the criticism.

"I don't know if I used those exact words, but that sounds about how I talk," Shanahan said. "When you're the coordinator of an offense or you're the head coach of a team, you're responsible for what happens out there. If a play doesn't go right, if a player misses something, that starts with the offensive coordinator when you're on offense. I did believe we had a very good chance to win that game, especially at the end, and we didn't get it done.

"In terms of using the words, 'I blew it,' I don't look at it that way. I believe we missed an opportunity. We didn't get it done. I'll go back through every play for the rest of my life."

Ex-Falcons OC Kyle Shanahan says he'll learn from the team's Super Bowl LI collapse going forward as the new Niners coach. AP Photo/Marcio Jose Sanchez

With Shanahan pegged to take the Niners job soon after the Super Bowl, the assumption was that he would be on a plane to San Francisco on Monday. Instead, Shanahan said 49ers CEO Jed York told him to take a day and a half to collect himself.

As a result, Shanahan spent Monday with his Falcons players.

"I was definitely grieving it, and I probably will for a while, but to be able to go up to the building in Atlanta the next day and get to talk to all the players -- all of us spent some time together -- and go through it again really gave us some closure on it," Shanahan said. "We put our whole heart and souls into that season, into that game. We did everything we could. I know the results weren't what we wanted; you've got to live with that. But I'm real proud of the coaching staff, myself, the players, that we did as good as we could.

"We had no hesitation, and we let it all out there. You've got to live with the results, but that's why we're in this business: You've got to take the good with the bad. I'm just very happy that I was a part of it."

As for how the late collapse will affect him moving forward, Shanahan acknowledged that it helps him knowing he stayed true to his aggressive approach.

"It's human nature when you get in big moments like that to lock up, to hesitate, to try to take the easy way out and make sure you don't get blamed," Shanahan said. "That's something that I wasn't going to do and people on our team weren't going to do. We played that game how we played the entire year, and I thought I called plays in that game the way I had the entire year.

"Doesn't mean I'm always right. Doesn't mean they're always going to work. But I promise you I prepare as hard as I possibly can. I always do what I believe is right with our coaching staff and the players, and then you live with the consequences."

"Yeah, it's going to be hard living with that loss," he added. "Every play that didn't work, I regret, as always. But I can deal with it, because I can look at myself in the mirror and know I did what I thought was right at the time, and that was the most important thing to me. I didn't change because of a circumstance. I did what I thought was right, but whatever happens, if you do what you thought was right and you believed in that because of the preparation you had, then you should be able to live with the consequences."