Mark Rzepczynski came in to pitch and Jay Bruce moved the runners up with a grounder back to the mound.
Homer Bailey (8-6) notched his third straight win for the Reds, allowing two runs (one earned) on nine hits over eight innings. He walked two and struck out two.
The Reds remained tied with the Pittsburgh Pirates atop the National League Central with their sixth straight win overall.
Westbrook finished by allowing four runs on nine hits in 7 1/3 innings.
Yadier Molina went 3-for-4 with a solo homer and two RBI for third-place St. Louis, which fell 4 1/2 games off the pace in the NL Central.