The Boston Red Sox have designated veteran pitcher Rich Hill for assignment to make room for 24-year-old right-handed pitcher Luis Guerrero on the active roster. Hill, who recently returned to the Red Sox at age 44 after a brief hiatus, struggled in his four relief appearances, posting a 4.91 ERA. Guerrero, who has been impressive in Triple-A Worcester with a 3.31 ERA and 79 strikeouts over 54 1/3 innings, will now join the major league team. Hill's future in baseball remains uncertain, but he leaves behind a 20-year career with a 90-74 record and a 4.01 ERA, having played for 13 different teams. The Red Sox, who were recently in the American League Wild Card conversation, now face a challenging path to the postseason.