SEATTLE — Mariners center fielder Julio Rodríguez has started running as he recovers from a high ankle sprain, but the team remains uncertain about when its young star will return to the lineup.

General manager Justin Hollander said Friday that Rodríguez has begun “running linearly” and is recovering “at a high rate.” Hollander said the nature of the injury makes it difficult to know when Rodríguez will be ready to make the cuts and lateral moves he will need to return to Seattle’s lineup.

“Julio is usually a fast healer and he’s younger, faster and stronger than almost everyone else in the world, so he’s doing the best he can. I know he wants to get back here,” Hollander said.

Rodríguez suffered an ankle injury on July 21 when he hit the center field wall while trying to catch the ball.

The update on Rodríguez came the same day Seattle placed relief pitcher Gregory Santos on the 15-day disabled list with biceps inflammation, with the hope that it will be a short-term one. Santos left the mound in the middle of the eighth inning on Wednesday after experiencing discomfort in his arm.

Seattle also picked up right-hander Jonathan Hernández off waivers from Texas and designated right-hander Brett de Geus for assignment. Hernández is 3-1 in 26 appearances for the Rangers this season and has a 5.05 ERA. He was designated for assignment by Texas on Tuesday.

Another uncertain timeline for Seattle is shortstop J.P. Crawford, who was out to catch ground balls before Friday’s game and is still recovering from a fractured little finger on his right hand. Hollander said Crawford will undergo another round of X-rays on Monday but will not see any progress in his baseball activities until Aug. 19 at the earliest.

“That’s going to be four weeks. That’s pretty aggressive, but that’s definitely the earliest. It just depends on what kind of recovery we see,” Hollander said.

Outfielder Dominic Canzone (adductor) began a rehab assignment Thursday at Triple-A Tacoma. Hollander said there’s a chance he could be activated during this home game. Canzone has been out since July 10.