Ronald Nored hit a tiebreaking layup and free throw with 25.4 seconds left, and Butler narrowly evaded 13th-seeded Murray State's second upset attempt in three days, advancing to the Sweet 16 of the NCAA tournament with a 54-52 victory Saturday.
Nored scored 15 points and Gordon Hayward had 12 before making the decisive defensive play for the fifth-seeded Bulldogs (30-4), who extended the nation's longest winning streak to 22 games.
Butler advanced to the round of 16 for the second time in four years - but only after surviving a thriller against the undersized but big-hearted Racers (31-5), who beat fourth-seeded Vanderbilt in the first round of the West Regional on a buzzer-beater.
Isaiah Canaan scored 14 points and hit four 3-pointers for the Racers. He had the ball on Murray State's last possession, but Hayward deflected his pass into the backcourt in the final seconds.
The Bulldogs will face either Syracuse or Gonzaga next weekend in Salt Lake City.