BOSTON -- Celtics All-Star point guard Kyrie Irving left Sunday's game against the Indiana Pacers with left knee soreness. Irving played 16 first-half minutes but did not return for the start of the second half. The Celtics ruled him out for the remainder of the game. Boston was already playing without All-Star big man Al Horford (illness) and Irving's typical backcourt partner,? Jaylen Brown (concussion). Irving battled left-knee soreness during Boston's recently concluded three-game road trip. After playing through discomfort in Houston, Irving sat out a visit to Chicago on Monday then returned for the Celtics' win in Minnesota on Thursday. During an appearance on Boston sports radio 98.5 the Sports Hub last week, Celtics president of basketball operations Danny Ainge suggested that knee soreness might be something that Irving would have to "manage the rest of his career." "I don't think it's anything serious, but we want Kyrie healthy...