On deck was Ryan Seacrest, recently named a prime-time host of NBC's coverage of the Summer Olympics in London, in town to interview him. And later that night, Phelps would headline a fundraising gala for Meadowbrook's North Baltimore Aquatic Club, mingling with the Maryland governor and first lady and donors who in some cases paid in the five figures to meet him.
A hundred days from Wednesday, the Summer Games will open, but the event is also the beginning of the end of one of the greatest Olympic careers ever. The demands both in and out of the pool are greater than ever before for the 26-year-old Phelps, but he says he is both excited and at ease heading into his fourth and final Olympics.
"I think the real biggest difference is that Bob and I are more relaxed now than we were," Phelps said, eliciting a speak-for-yourself reaction from his longtime and famously intense coach, Bob Bowman, as they launched the black-tie event at M&T Bank Stadium. "That's probably the real big change."
For those in the world of swimming, and the multitudes who have been drawn to it by Phelps' dazzling Olympic performances, London approaches as something of a bittersweet event. Phelps himself has acknowledged both the pride and the sadness that he feels as he puts this final cap on his competitive swimming career.
But the nostalgia comes with no small measure of anticipation. While Phelps has been adamant that he won't duplicate his 2008 program in Beijing, a record-breaking 8-for-8- gold-medal performance, he has slyly refused to reveal just how many and which races he'll enter in London.
Cue the speculation, layered with the wishful thinking of those eager to be dazzled one more time by Phelps.
"This is my gut feeling and also snooping around a little bit — seven events," said Rowdy Gaines, the three-time Olympic gold-medalist and NBC swimming analyst, guessing four individual races and three relays.
As for the number of medals Phelps might bring home, Gaines expects "as many events as he swims," even if they're not all gold.
It's hard to overstate Phelps' importance to his sport, the Olympics and even NBC's ratings. In 2008, viewership jumped every night that he swam and dropped when he didn't. At least one industry analyst says he expects viewers to tune in again for the sequel.
"The Olympics thrive on storytelling," said Larry Gerbrandt, who heads Los Angeles-based research firm Media Valuation Partners. "We haven't had too many other athletes in recent years where you could link them back to a previous Olympics. When you have a back story like Phelps', and they can build it up — 'Can he do it again?' — this is grist for the mill. This is what Olympic broadcasters do best."
The drumbeat is already starting. The U.S. Olympic Committee is celebrating the 100-days-out point by creating a mini-Olympic Village in Times Square on Wednesday, featuring such potential London stars as Missy Franklin, the powerful 16-year-old swimmer from Colorado who is the latest so-called "female Phelps."
Phelps' teammate the past couple of Olympics, Natalie Coughlin, said Tuesday that "it is insane" to find herself just 100 days from London. In a conference call with reporters, she called Phelps' focus and drive "amazing."
"He has a lot of pressure going into London," the 11-time Olympic medalist said. "But he has nothing to prove. He's the greatest swimmer that we've ever seen. Everything he does in London is just going to be bonus for him and all of us who get to watch."
Olympic commentator Mel Stewart, a gold and bronze medalist in the 1992 Games, agreed that after Beijing, Phelps already is "hovering in the stratosphere."
"I think what's astonishing is he came back," said Stewart, who last month launched a popular news and commentary website, swimswam.com. While Phelps acknowledges that it took him some time after Beijing to renew his commitment and training, by this year, Stewart was among those who were cheered to see him return to form this year.
Stewart points in particular to Phelps' 200-meter freestyle win in the Columbus (Ohio) Grand Prix swim meet in March as a turning point.
"He has not looked like that since '08. He was swimming high in the water with strength and such a nice flow and command of stroke," Stewart marveled. "The way he was kicking, his stroke cycle, it was: Oh, my God, Michael is back."
Phelps created more buzz at the Indianapolis stop of the Grand Prix series last month when he won the grueling 400-meter individual medley, the so-called decathlon of the sport that combines all four strokes. Stewart thinks Phelps could add this event to his London lineup and even go 8-for-8 again, although he concedes that's his heart talking.
"We are so emotionally attached to this guy," Stewart said of the gratitude swimmers feel for how Phelps has elevated the sport.
To illustrate his role in swimming's greater popularity post- than pre-Phelps, Gaines points to the fact that this year, for the first time, NBC will cover every night of the U.S. Olympic swimming trials in Omaha, Neb., that begin June 25, and selected Grand Prix events.
"We only cover the ones Michael's swimming in," he said. "Of course, everyone else receives the benefits of that, but my point is … it's because of Michael, pure and simple. He's grown the sport."
Who might stand between Phelps and multiple trips to the medal stand is also subject to much pre-Olympic speculation. His closest American competitor is Ryan Lochte, who despite a mostly lackluster performance at their last meeting, in Indianapolis, beat him several times in head-to-head matchups in previous years.
A fast Australian team, led by current sensation James Magnussen, is headed to London and poses the biggest threat to U.S. swimmers repeating past gold-medal victories in the always-exciting relay races.
But back in Baltimore, Team Phelps says that even just 100 days out, it's too soon to call favorites going into London.
"We'll have to wait and see," said Bowman, who will be one of the coaches of the U.S. Olympic swim team. Bowman said that because the U.S. trials come later than many other countries, it's impossible to say how the relay teams will stack up against one another.
In other words, first things first. Both he and Phelps say the trials are harder than the Olympics, so that is what where their current focus lies.
"They're very stressful," Bowman said, speaking by phone from a practice at Meadowbrook this week. "You get one chance. Once you make the Olympics, you can almost relax. The goal is to be there. The thought of not making the Olympics is very powerful. Even the best people can't rest on their laurels."
Phelps, for his part, says there's only one thing he can control en route to London.
"I can only prepare myself," he said before the Saturday fundraiser. "I'm only in charge of myself. I know Bob and I can get the job done."
July 27-Aug. 12
Swimming events: July 28-Aug. 4
Medal sports: 26
Medal events: 302
Notable new events: Women's boxing (three weight classes), mixed doubles in tennis and Omnium racing in track cycling