Asked by the Post-Dispatch if he had seen Arroyo go to his cap, Duncan said, "Just every pitch."
Smoltz allowed five walks and six runs over his four innings after he came in with only four walks over his previous six starts. He repeatedly tossed balls out of play because he felt they were too slick to grip in the frigid conditions at Great American Ball Park.
"I've been around for 40-plus years now, and I've never seen a Major League baseball game played with balls like that," Duncan told the Post-Dispatch.
After Smoltz departed, three Cardinals pitchers worked the remaining four innings scoreless, and there were no complaints about the balls.
"He shouldn't make wild accusations like that," Reds pitch coach Dick Pole said Thursday of Duncan. "If they suspected that last night, why didn't they check him? They would find nothing. The balls [Smoltz] were throwing out looked fine to me."
Before games, it's the home clubhouse staff's responsibility to apply mud to the baseballs so pitchers can get better grips.
Arroyo also denied the allegations levied by Duncan.
"The reason he's saying that is because I've been using this hat all season," Arroyo said. "That's what happens from playing games in every other park, where there is so much mud on the balls. That black stuff comes off on my fingers every day."
Arroyo produced the game cap from his locker and the bill was stained black.
"The funny thing is I normally switch out hats. I have two hats," Arroyo said. "The other one is a lot cleaner. It's starting to build up a little bit. I didn't switch hats because it wasn't hot enough to be really soaked and wet like in the summertime."
Reds manager Dusty Baker wasn't aware of the Duncan accusations until informed by reporters Thursday.
"If anybody should know, it would be Duncan," Baker responded. "I remember they had Julian Tavarez over there. They threw his hat out, remember that? His hat was all messed up. They also had a left-hander, Steve Kline. It's not like it's something new."
Tavarez, a former Cardinals pitcher, was ejected from a game in 2004 for having a dirty cap with pine tar on it.
As for the Duncan comment about going to his cap with his right hand frequently, Arroyo was nonplussed.
"I have 8,000 twitches," Arroyo said. "What do you want me to do about it? That's how I pitch. The next time I pitch, I guarantee that I will call over there on the phone say, 'Dave Duncan, this is Bronson. I'm putting on a brand new hat.'"
With his final outing behind him, Arroyo finished with a 15-13 record and a 3.84 ERA in 33 starts. His 220 1/3 innings gave him five straight 200-innings seasons.
No stranger to pitching in cold weather, Arroyo pointed out that he pitched before in the postseason at Yankee Stadium in October when the balls were very difficult to grip.
"Every ball is different," Arroyo said. "Sometimes you hate them. Sometimes you don't. What are you going to do? You throw what you've got. You find a way to pitch."