After walking two and giving up a three-run homer to Trevor Plouffe in Thursday's 9-6 loss to the A's, Altavilla's ERA rose to 7.36 in nine outings.
Altavilla, 24, performed extremely well in a late-season callup last season, with a 0.73 ERA in 12 1/3 innings over 15 appearances. He is ranked as Seattle's No. 8 prospect by MLBPipeline.com.
De Jong made his Major League debut against the Astros on April 5 in the Mariners' third game of the season and got two outs in the 13th inning before surrendering a three-run walk-off home run to George Springer after Seattle had taken a 3-2 lead in the top of the inning.