Bruce Springsteen is joined by Zach Bryan on stage at the Triumphant Brooklyn Show

Zac Bryan has never hidden his deep love for Bruce Springsteen, so there was no reason to believe he was sending any hidden message when he used “Johnny 99” as his background music Wednesday night in Brooklyn at the Barclays Center, or even when he took the stage in a Springsteen tour T-shirt with the sleeves cut off. But when Bryan began his two-song encore with the chords of his unreleased song “Sandpaper,” Springsteen himself walked onstage without warning.

As the stunned crowd cheered, the two men traded lines on the song's lyrics and harmonized on the choruses (“they've been trying to smooth me over for 27 seasons now”), with Springsteen taking the high parts. From there, Bryan launched into his usual show, “Revival,” and Springsteen remained onstage, where he was joined by Maggie Rogers, who had appeared in a duet with Bryan on “Dawns” earlier in the show.

Bryan usually introduces his band during “Revival” and added an extra member Wednesday night: “His name is….Springsteen!” As Bryan's band rolled through “Revival,” Springsteen sang both on and off the mic, sometimes sharing one with a clearly ecstatic Rogers tambourine. Springsteen also played a brief but impressive guitar solo and even joined the others players for some choreographed moves.

The legend's appearance was a major show of respect for the younger artist — Springsteen is in the middle of a West Coast run with the E Street Band and flew back east to play with Bryan — learning “Sandpaper” on the day of show, according to a source familiar with the logistics of the concert. Springsteen then had to fly right back to California to play a concert in San Francisco on Thursday night.

Elsewhere in the show, between the crowd's surprisingly loud sing-alongs to his hits, Bryan played more unreleased songs (“The Great American Bar Scene” and “Better Days”) from a new album he said will be released later this year.