The Red Sox put reliever Hector Velazquez, who pitched four innings in a 17-inning loss to the Twins Tuesday night, back on the injured list with a lower back strain.
Velazquez had just returned from the IL on Monday. He allowed one run on three hits with three strikeouts over 4 relief innings, his first appearance since being reinstated from the 10-day injured list, and had a blown save, allowing a 13-inning homer to Twins rightfielder Max Kepler.
Velazquez, 30, has made 19 appearances (seven starts) for Boston this season, posting a 5.59 ERA and a 1-3 record.
Smith, 31, has made eight appearances (two starts) over three stints with Boston this season, going 0-2 with a 6.28 ERA. He picked up his first major league save on June 13 against Texas.