Volquez went on the 15-day disabled list after back spasms forced him from a game on May 16 in San Diego. He threw 87 pitches on Wednesday without problem. He will throw in the bullpen again on Saturday and if his back is fine, the Reds will plan to activate him for a start Monday in St. Louis.
"I think I'll be ready to go for my next start," Volquez said.
Volquez won 17 games last season, when he was the Reds' only All-Star. They called up right-hander Homer Bailey to take his place when he went on the disabled list, then sent Bailey back to Triple-A after he struggled in his only start. Bailey failed to last five innings during a 7-6 loss to Cleveland on Saturday.
Third baseman Edwin Encarnacion plans to accompany the team to Milwaukee for a weekend series and take batting practice for the first time since he broke his left wrist on April 27. Encarnacion chipped a bone on a swing.
There's no timetable for his return. He resumed playing catch this week.
"It felt great. No problems," Encarnacion said Wednesday.
The wrist had been sore since spring training, limiting him at the plate. Encarnacion is batting .127 and was in a 1-for-28 slump when he struck out in the ninth inning of a 4-1 loss to Houston, hurting the wrist on his last swing. He had hoped to be back before the end of May.
"I never expected it to take this long," he said.
Second baseman Brandon Phillips, who suffered a hairline fracture at the tip of his right thumb on Saturday, could be back in the lineup during the series in Milwaukee.