The majors are another matter.
Encarnacion improved to 4-for-6 -- with all the hits home runs -- with six RBI in his career against Reyes.
"In the minor leagues, he was one of the nastier pitchers that I faced," said Encarnacion, who has 13 home runs this season. "I just see the ball and hit it."
Arroyo allowed one run over six innings and Brandon Phillips also homered for the Reds as St. Louis missed an opportunity to close in on first place in the NL Central and left manager Tony La Russa befuddled.
"What am I going to do, yell and scream at them?" La Russa said. "I don't see anyone not trying. We all share the responsibility."
The Cardinals are four games behind division co-leaders Milwaukee, which lost 7-4 at Pittsburgh, and Chicago, which beat Houston 3-2.
Arroyo (9-14) allowed six hits with no walks and five strikeouts in six innings to pick up his fourth victory in his past five decisions. He improved his career record in September to 14-6.
"It's the end of the season," Arroyo said. "Maybe the other guys are getting a little tired. I always feel good down the stretch. It's cooler. Obviously, you want to finish off strong. You want to feel like you've given your team consistent work."
The Cardinals had runners on first and third with no outs in the second, but Reyes bunted through a pitch for strike three and Aaron Miles struck out swinging before David Eckstein flied out to end the threat.
"You've got to give Arroyo credit," La Russa said. "A lot of times, we blame the pitching, but we only scored one run tonight, and we needed six."
Phillips gave the Reds a 1-0 lead in the fifth when he hit a 3-2 pitch down the left field line and into the first section of seats in fair territory for his 29th home run, and first in 18 at-bats since Sept. 5.
After Adam Dunn walked, Encarnacion launched a 3-1 pitch from Reyes 437 feet into the upper-deck bleachers in left.
"Eddie hit that ball really well," Reds manager Pete Mackanin said. "You can see he looks comfortable at the plate. You can tell he's where he really wants to be. He's doing more like what we expected of him all along."
Reyes (2-14) went 3 1/3 innings, allowing four hits and three runs with two walks and a strikeout in his first start since Aug. 31.
"I started pretty good, then it started slipping away," Reyes said. "I was making pitches, then I hung a couple. I was trying to go with my curveball, trying to get them to hit into double plays."
- Reds SS Alex Gonzalez, who missed the previous two games after leaving Saturday with a left leg injury, left after the third inning with a sore left knee.
- Cincinnati CF Josh Hamilton left after five innings with a strained right hamstring. He missed games Saturday and Sunday against Milwaukee with tightness in his hamstring.
- The Reds said 350 dogs -- and their owners -- were at the game, located in special sections on field level down the right field line, as part of a special promotion
- The Reds completed the Aug. 30 trade with the Cubs for OF Buck Coats and cash by sending minor-league RHP Marcos Mateo to Chicago.