Kiermaier is hopeful of missing just a couple of weeks after an MRI exam Sunday found the ligament intact and no surgery required.
"It's the best news I could have received given what happened," Kiermaier said. "I'm going to be OK. I'm going to be back out on the field sooner than later."
Kiermaier was hurt diving headfirst into first base on an infield single in the eighth inning of the Rays' 2-1, 11-inning loss to the Chicago White Sox on Saturday night.
The Rays lost for the 21st time in 36 games and have fallen behind Cleveland and Oakland in the AL wild-card race.
"Everything I do on the field I do for a purpose," Kiermaier said. "Right now we have a struggling team and things haven't been going our way a whole lot lately. This is when I want to play harder, I want to play with more passion."
This is the fourth consecutive year the standout defender has been sidelined by sliding or diving injuries.
Kiermaier missed 57 games last season due to a torn right thumb ligament that occurred while sliding into second base.
He missed 61 games during the 2017 season after fracturing his right hip sliding awkwardly into first base on an infield hit attempt.
Kiermaier fractured his left hand diving for a ball in 2016 and missed 48 games.
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