McClendon said the 26-year-old will need several Minor League outings before he rejoins the Mariners. Tacoma hosts Memphis on Sunday at 5:05 p.m. PT to kick off an eight-game homestand.
"I'd say he'll need at least two rehab starts. In all likelihood three, but we'll see," McClendon said prior to Wednesday's series finale with the Rangers.
Either scenario would set Paxton up to rejoin Seattle in early September, with a chance to make four or five starts before the season ends.
Paxton opened the campaign as Seattle's No. 2 starter and went 3-3 with a 3.