CLEVELAND -- Guardians All-Star left fielder Steven Kwan is scheduled to undergo tests on his back after he was scratched from Friday night's game against Tampa Bay.

Kwan was in Cleveland's original lineup, batting in his familiar leadoff spot. However, about two hours before the first pitch, the Guardians said Kwan would not play with what the team initially said was "body fatigue."

Following the Guardians' 3-1 loss to the Rays, manager Stephen Vogt said Kwan was dealing with "back soreness" and would undergo tests. It wasn't clear if Kwan has already gotten them or will have them Saturday.

Kwan missed four weeks with a hamstring strain earlier this season. The 27-year-old has dealt with hamstring issues, dating to his time at Oregon State.

In just three seasons, Kwan has blossomed into one of the AL's best top-of-the-order hitters. He flirted with .400 for the first two months and was leading MLB in batting average (.352) at the All-Star break.

But he has been in a prolonged slump in the second half. He is batting .291 amid a 6-for-39 slide.

A two-time Gold Glove winner, Kwan also has been solid in the field. He recorded his ninth assist in Thursday's game.

Rookie Daniel Schneemann took Kwan's spot on Friday and went 0-for-3 with two strikeouts.