Walden stopped warming up in the eighth inning Saturday. He's 0-1 with an 0.87 ERA in 12 games with 12 strikeouts in 10 1-3 innings.
The 22-year-old Tuivailala has three saves and has not allowed an earned run in eight appearances covering nine innings at Memphis. The saves have come in his last three appearances.
Tuivailala was a third-round draft pick in 2010.