According to the News Tribune's TJ Cotterill, manager Scott Servais said Cruz twisted his ankle slipping on the steps when he returned to the dugout following a home run in the sixth inning at Safeco Field.
Despite this setback, Cruz has been durable in recent years and played at least 152 games four straight seasons from 2014 through 2017.
The five-time All-Star is one of the best power hitters in the league when healthy. He drilled 40 home runs in 2014, 44 in 2015, 43 in 2016 and 39 last year and is 2-for-6 with two home runs and four RBI in 2018.
While the Mariners can turn to Daniel Vogelbach to play designated hitter during Cruz's potential absence, they can't realistically expect him to replicate the production the normal starter does on a nightly basis.
Seattle likely needs Cruz back and healthy as one of the anchors of its lineup if it hopes to challenge for an American League West crown this season.