Rivera has been nursing a right triceps injury, missing a three-game set in Cleveland earlier in the week before pronouncing himself ready to pitch Thursday before the Yankees' home series versus the Tampa Bay Rays. The 23-year-old Walden, 18 years Rivera's junior, was the next highest-ranking relief pitcher on the players' ballot.
Walden is 1-2 with a 2.95 ERA and has converted 19 of his 25 save chances this season. The hard-throwing right-hander is the first Angels rookie to make the All-Star team since pitcher Jason Dickson in 1997.
Walden had to cancel his plans to go fishing at Big Bear Lake with fellow Angels reliever Bobby Cassevah during the All-Star break. His parents made last-minute arrangements to travel from Forth Worth, Texas, to watch the July 12 game at Arizona's Chase Field.
"I was very surprised," Walden said of being selected. "My numbers aren't too good, so I didn't expect to be an All-Star. But I'm happy and ready to play in it."
Walden supplanted Fernando Rodney as the Angels' closer in April. He began the 2010 season at Double-A Arkansas and made just a brief stop at Triple-A before making his major league debut with the Angels last August. Walden occasionally breaks the 100 mph barrier with his fastball.
Rivera has not been available to pitch for the Yankees the past three games in Cleveland because of soreness in his triceps. He pronounced himself ready to pitch Thursday before the Yankees' home series versus the Tampa Bay Rays.
Mark Saxon covers the Angels for ESPNLosAngeles.com.