Ryan, 37, hasn't played in the majors this season but could be a September call-up if he shows some power at the plate. He would be eligible for the postseason roster if the Rockies qualify for the playoffs.
Howard hit 382 home runs for the Phillies in 13 seasons, then became a free agent and signed a minor league contract with Atlanta. He was released by the Braves after he hit .184 in 11 games at Triple-A.
Howard was the NL Rookie of the Year in 2005 and MVP in 2006, and he led the Phillies to the 2008 World Series title. He tore an Achilles tendon when he grounded out for the final out of the 2011 NL Division Series loss to St. Louis.