The Orioles initially said Flaherty have been optioned to Single-A Frederick.
The Shorebirds are home against Kannapolis the next two nights before finishing the season at Hickory.
Flaherty will become the first major league player to suit up for Delmarva in 2013. The Shorebirds will make a corresponding roster move on Wednesday to open a spot for him.
Frederick is currently on the road and doesn't return home until beginning a three-game series against Potomac on Saturday that concludes its season.
Flaherty is expected to join the Keys for that series before the Orioles recall him as part of their expanded roster.
Meanwhile, the Orioles continue to trail the Red Sox 11-2 at Fenway Park. Troy Patton struck out two while retiring the side in order in the bottom of the sixth.
Update: The Orioles have allowed their most runs this season, as they trail the Red Sox 13-2 in the top of the eighth.
The 11-run margin ties the largest this season. The Astros beat the Orioles 11-0 on July 31.
Brian Matusz gave up two runs in the bottom of the seventh tonight after retiring the first two batters. Shane Victorino had a two-run double, giving him a career-high seven RBIs.
Update II: Manager Buck Showalter is clearing his bench.
Taylor Teagarden pinch-hit for Chris Davis and replaced Matt Wieters behind the plate. Wilson Betemit replaced Davis at first, making his 2013 debut. Alexi Casilla is playing shortstop, and Danny Valencia is playing third base. The Orioles have surrendered their designated hitter.
Nate McLouth replaced Adam Jones in center field. Casilla was on deck to pinch-hit for Jones when Teagarden made the final out in the top of the eighth.
Francisco Rodriguez is pitching.
Update III: Game over. The Orioles lose to the Red Sox 13-2.
Betemit got his first at-bat for the Orioles this season, bouncing out to second to end the game.