Clevenger said Friday he knew he was wrong, and he apologized to Sveum after a 5-3 comeback win over the Reds.
"Dale was right: I can't get ejected in that situation for that," Clevenger said. "I went up and apologized to Dale last night for getting ejected. Like I said, won't happen again, can't happen."
With a runner on first, one out and the Cubs trailing, 3-1, Reds right-hander Mike Leake threw a 1-1 fastball to Clevenger, who took the outside pitch, which was ruled a strike by Nelson.
The previous pitch, called a ball, was in a similar spot, and TV audio picked up Clevenger telling Nelson, "That was the same [gosh darn] pitch."
Clevenger -- who also appeared to be upset when he was called out looking in the second inning -- was then ejected.
"The ball was outside, and the next pitch was the same exact pitch, I thought, and he called it a ball," said Clevenger, who reiterated he was sorry.
"In the heat of the moment, you say things you regret," Clevenger said. "I'll talk to Jeff. I'm sure I'll have him behind the plate sometime this year or somewhere."