The comeback made a winner of Bronson Arroyo (8-7), who held the Cubs to two runs and five hits over eight innings. Arroyo gave up both runs early, but settled down to improve to 5-0 in his last seven starts at Wrigley Field.
"With a runner on third, especially when I got to two strikes, I was just trying to put the ball in play," Ludwick said. "I didn't want to strike out and obviously I was fortunate enough to hit the double and get two (runs) instead of one.
"Big hit being able to get Bronson a win and win two in a row after losing those five."
Ludwick has driven in 28 runs since the All-Star break to go along with eight home runs.
"He's deserved everything he's gotten," Reds manager Dusty Baker said. "Once a veteran guy gets his stroke, once his confidence level is high, he can continue that for an extended period of time."
Reds closer Aroldis Chapman continued his recent dominance by setting down three straight in the ninth and converting his 27th save, including his 19th straight.
Chapman last blew a save on June 24. He's thrown 20 2/3 scoreless innings and struck out 44 since.
Before the game, the Reds announced Votto had flown from Chicago to Cincinnati Friday after feeling soreness in the left knee he had arthroscopic surgery on July 17. The 2010 NL MVP had a minor procedure to remove a piece of floating cartilage, but will likely miss an additional week. The Reds don't expect him back until mid-August now.
"I think everyone in here is praying and wishing he can get back as soon as possible because we definitely need him on our team, but I think some of the guys have taken it as a challenge to pick one another up," Ludwick said.
Cubs starter Travis Wood held Cincinnati to five hits and matched a career-high with eight strikeouts but finished with a no-decision despite leaving with a 2-1 lead. Wood had posted an 8.78 ERA in losing his previous five starts.
David DeJesus provided the offense for Chicago, stroking a two-out, two-run single off Arroyo in the second inning.
Russell allowed three runs and five hits in the eighth, and the Cubs lost for the 10th time in 11 games.
The first-place Reds have won two straight after snapping a five-game losing streak on Friday. Cincinnati's 21-8 mark since the All-Star break is the best in the majors.
After DeJesus singled up the middle just past Arroyo to plate the Cubs' runs in the second, the Reds' right-hander retired 12 straight hitters.
Despite his recent struggles, Wood was sharp in his first appearance against his former team. He was dealt to the Cubs during the offseason for LHP Sean Marshall after going 11-10 over two seasons with Cincinnati.
The only run against Wood came in the fourth on an RBI double by Frazier.
Manager Dusty Baker said Votto felt soreness in his knee after participating in a sliding drill. The 2010 NL MVP was injured while sliding into third base on July 17. ... Baker said slumping OF Jay Bruce will be back in the Cincinnati lineup on Sunday. Bruce is 1 for his last 16 with seven strikeouts. ... The Cubs activated RHP Lendy Castillo from the disabled list and optioned LHP Scott Maine to Triple-A Iowa. ... Chicago promoted Tim Wilken to a role as a special assistant to general manager Jed Hoyer and team president Theo Epstein. Jaron Madison was hired from the San Diego organization to take Wilken's place as director of amateur scouting.