Hagar is now on MLB.com, where you can sample 11 tracks on the upcoming collaborative album. You can also purchase the "Knockdown Dragout" track featuring Kid Rock, Joe Satriani and Denny Carmassi, view a photo gallery and watch that Nationals Park video performance.
"Early on in my career, St. Louis was the first place I ever headlined a baseball stadium," Hagar said. "Back in '79, Busch Stadium, I headlined for 44,000 fans, and it was the thrill of my life. It was the first city where I felt: I could play a baseball stadium.
"And then playing the Nationals' stadium was really cool. It's like they didn't necessarily all pay to see me -- they paid to see a great baseball game, and at the end of it, they all stayed. That was the cool part of it. You expect out of 35,000 people, you'll end up playing for 5,000 fans or something. But I played for about 30,000 people, and that was really exciting."
In that postgame concert spanning four decades of rock, Hagar performed vocals and guitar along with David Lauser on drums, Mona Gnader on bass/vocals and Vic Johnson on guitar/vocals. You'll see another familiar face on stage, as Michael Anthony -- Hagar's past band partner with Van Halen and Chickenfoot -- makes a special guest appearance on bass and vocals.
"I had to squeeze 40 years of rock and roll into one hour," Hagar said, "which was a little bit difficult picking the songs. But once we were done, I felt like I'd done the right thing. ... You're going to get to [see] a live version of 'Knockdown Dragout,' which is great."
In addition to Kid Rock, Satriani, Carmassi (Montrose) and Anthony, other artists who collaborated with Hagar on the new album include Mickey Hart (Grateful Dead), Neal Schon (Santana, Journey and HSAS), Chad Smith (Red Hot Chili Peppers and Chickenfoot), Taj Mahal, Ronnie Dunn (Brooks & Dunn), Toby Keith, Nancy Wilson (Heart), Bill Church (Montrose) and The Wabos.
"The thing about my new album which makes me most proud and so excited about is, I got to work with some of my heroes -- friends I've known forever but not necessarily worked with all the time," he said. "The Cabo Wabo Birthday Bash, a lifestyle down there [in Cabo San Lucas], has allowed me to play with so many different people for the last 23 years. So I just kind of used that as a boilerplate, and 'Oh, Toby's coming to Cabo.' And 'Oh, Neal Schon's been to Cabo years ago and we've jammed before.' So I kind of brought as many people back together at one time.
"That's the most exciting part about 'Sammy Hagar & Friends.' It's really the life I'm living right now, and I just made a record that way -- it's pretty special."
In 2011, Hagar's autobiography, "Red: My Uncensored Life in Rock," became just his latest No. 1, this time on The New York Times bestseller list. He wrote an afterword for the ensuing paperback version, and in that, he waxed philosophical about the whole point of charging on. "What else do I need to do?" he asked in the book, feeling "satisfied" at that point.
But whenever those thoughts creep into his head, that is about the time you find him at a National League East ballpark, screaming at the top of his lungs with a standing crowd on a summer night so muggy, Gonzalez had to change jerseys in the middle of his start. Hagar said he "should have changed my T-shirt after every song, because it was muggy out there, definitely hot. But you know, hot better than cold."
The son of a shaken World War II vet and steel worker, Hager has a hard-working ethic that keeps him going, no matter what.
"Every time I do a new project, no matter what it is, it seems like I always get inspired to do another one," Hagar told MLB.com. "Almost every project I do, I do it as if it's the last one. When I wrote my book, I really thought, 'OK, I'm writing my book now, so now I'm kind of done.' And then something happens that inspires you to keep going.
"To end up at this stage of my life after having more success than I ever completely ever dreamed of in a billion lifetimes, I still love doing it. So I'm standing up in front of Nationals Park with thousands of baseball fans playing a concert, [and] it's just as exciting as the first concert I ever played in. It's always fun, it's always great, I love to play music."
One might draw a comparison to Tony Bennett, an American institution who recorded "Duets II" in 2011 and then took a Grammy Award for Best Traditional Pop Vocal Album. Maybe Hagar will find similar success with this collaborative effort, one that summons his best reach, perhaps most notably on the piercing and powerful "Father Sun" track.
But what then? What beach, Cabo or otherwise, could hold the Red Rocker?
"I would love to retire," he wrote. "To me, retirement means flying around the world, going where I want, staying as long as I want, moving on when I want. Rome, Hong Kong, Madagascar, wherever. No schedule, no itinerary, no plan. That's retirement to me. I don't think I'm ever going to get to do that."