Plouffe was scratched from Monday's game against the Dodgers with left intercostal tightness, Levi Weaver of The Athletic Dallas reports.
Christian Lopes will step in to start at third base in Plouffe's place. The severity of the issue remains unclear, but more should be known shortly after he's further evaluated. It would be a tough break for Plouffe if he's forced to miss a chunk of time, as he's competing for a reserve role in camp following a disappointing 2017 campaign that saw him post a .198/.272/.318 line across 100 games between Oakland and Tampa Bay.