Sewald had his contract selected from Triple-A Syracuse on Friday.
The 29-year-old returns to the major-league bullpen after being designated for assignment in late May but remaining with the organization. In 19 appearances with Triple-A Syracuse this year, Sewald carries an ERA of 3.35 with a 52:15 K:BB over 51 innings. Drew Gagnon was optioned to Triple-A and Tim Peterson was designated for assignment in corresponding moves.