The San Diego Padres recalled right-hander Reiss Knehr from Triple-A El Paso on Sunday and optioned right-handed knuckleballer Matt Waldron one day after he made his major league debut.

Knehr, 26, returns to the Padres after posting a 12.27 ERA in three relief outings earlier this season. He is 1-2 with a 5.24 ERA in 20 career outings (six starts) with the Padres over the past three seasons.

Waldron, 26, gave up two runs on four hits over 4⅔ innings of his MLB debut Saturday against the Washington Nationals in a game San Diego lost 2-0.

Waldron was making a spot start for Michael Wacha, who was given additional rest to deal with shoulder fatigue.