Right-hander Casey Lawrence and outfielder Guillermo Heredia were recalled Tuesday from Tacoma of the Triple-A Pacific Coast League.
Ramirez strained his teres major, a muscle in his right rotator cuff, and Mariners manager Scott Servais said he likely will miss at least a month. Left-hander Wade LeBlanc will start in Ramirez's place on Thursday against Oakland.
Servais said the club didn't know whether Ramirez's injury was related to a lat strain earlier this season.
Altavilla has inflammation in the AC joint of his right shoulder and was put on the DL retroactive to Monday. Servais said he expected Altavilla to rest for four or five days, then determine whether to resume throwing.