His new boss, same as the old boss, grinned right back while bundled in a blue parka and knit cap with a pom-pom on top.
Were the reunited duo just happy to be working together again on Tuesday, a combo that had New England just one minute away from an unbeaten season four years ago?
Or were they chuckling over having pulled off a fast one — allowed though it is by the NFL — that could help the Patriots in Saturday night's divisional playoff game against the Denver Broncos and beyond?
McDaniels did coach the Broncos in all of 2009 and the first 12 games of 2010 before being fired with a 3-9 record.
Now, after the Rams released him from the final year of his contract as coordinator of an anemic offense, McDaniels is an offensive assistant on a team that could be headed for the Super Bowl, the same team he served as offensive coordinator from 2006-08.
One day after saying McDaniels has "some inside information" on the Broncos because he coached them, quarterback Tom Brady was asked about having him back in the meeting room.
"It's the same preparation for me," a subdued Brady said Tuesday. "We have some familiarity with what they do, obviously, playing them four weeks ago."
Brady threw for 320 yards and two touchdowns in that 41-23 win on Dec. 18 in Denver. He saw up close how linemen rush and cornerbacks cover. That's knowledge he can take into Saturday's game, something McDaniels didn't see.
And Brady, not McDaniels, has to make the game plan work.
In 2007, he threw for an NFL record 50 touchdowns and the Patriots were 18-0 before losing the Super Bowl to the New York Giants 17-14 on a last-minute touchdown. This season, they were 13-3 without McDaniels, while Brady threw for 5,235 yards, second most in NFL history.
In this digital football age of detailed computer and video analyses, one new coach may not add substantially to a team's knowledge of an opponent.
"Occasionally, people are hired off a staff that has been broken up because the head coach has been fired," said Gil Brandt, an NFL consultant and former general manager of the Dallas Cowboys. "But I don't think in today's NFL atmosphere it makes for any advantage. Maybe in the old days it did, but now we have tape and we can pull up any situation we want on any player or team. So the effect is minimal at best, I think."
Besides, McDaniels has been away from Denver for more than a year. John Fox, the current coach, has changed systems and players and doesn't seem worried.
"We're going to go play Carolina next year," said Fox, the Panthers' former coach. "I don't think that's going to be a huge advantage for me."
His players brush off suggestions McDaniels will reveal team secrets.
"I think everything to know about us is on film," wide receiver Eddie Royal said.
"We're just worried about ourselves," added running back Lance Ball. "We're not worried about what (McDaniels) thinks, what he's going to say to them. We're just worried about going in and beating the Patriots."
But a little tip here and there could pay off at a critical moment. After all, he was head coach when the Broncos drafted defensive end Robert Ayers in the first round in 2009 and quarterback Tim Tebow and wide receiver Demaryius Thomas in the first round in 2010.
Ayers is grateful to McDaniels for picking him, but is it fair for a coach who didn't make the playoffs with one team to join another for the postseason?
"I'll let you guys answer that one," Ayers told reporters. "I'm pretty sure I'm thinking the same thing you guys are thinking. I'm just not going to say it."
Fair or not, there's no NFL rule prohibiting it.
"Teams can sign, during the season, players, coaches, or other staff that are out of work and have no contractual obligation to another team," NFL spokesman Greg Aiello said.
Brandt, Cowboys general manager from 1960-88, first worked in the NFL as a part-time scout with the Los Angeles Rams in the late 1950s. In all that time, he can't remember such a case.
There was a similar one when Paul Pasqualoni was fired on Jan. 11, 2010 after two seasons as defensive coordinator of the Miami Dolphins. Four days later, he was hired to replace Dallas defensive line coach Todd Grantham, who had agreed to go to Georgia as defensive coordinator. And two days after that, the Cowboys lost an NFC divisional game to the Minnesota Vikings 34-3.
The Patriots hired the 35-year-old McDaniels on Sunday after the Rams finished their season at 2-14, leading to the firing of coach Steve Spagnuolo. He'll help offensive coordinator Bill O'Brien, who will stay through the playoffs before going to his new job as head coach at Penn State, with McDaniels expected to replace him in New England next season.
They worked together in 2008 in O'Brien's first year with the Patriots as wide receivers coach. They're described as good friends.
"He's ready to help us in any way that he can. I'm sure that he'll be an asset to our coaching staff and our team," Belichick said of McDaniels. "I'm not sure exactly how that will pan out."
Teams sometimes sign players to their rosters or practice squads to get inside information on an opponent it's about to play. Last season, the Patriots signed running back Danny Woodhead on Sept. 18, just 12 days after he was released by the New York Jets and one day before the teams faced each other.
Did it help? The Jets won 28-14.
And Woodhead was no stopgap; he's still with the Patriots.
McDaniels knows many Broncos players very well, but the roster has changed since he left.
"Now, if he had been in Denver this year, that would be a lot different," Brandt said, "if he was involved with the play-calling and the signals and that. But everything has changed there with the new (coaching) staff.
"I don't think there is an advantage one way or the other."
AP Pro Football Writers Arnie Stapleton in Denver and Barry Wilner in New York and Sports Writer Pat Graham in Denver contributed to this report.