Umpires said they found pine tar on his glove Tuesday night, the Tampa Bay Times reported. Peralta acknowledged the substance was there but said it got into his glove by accident since he uses the same one for batting practice.
Peralta could be suspended for at least 10 games.
Tampa Bay, playing in Washington, still beat the Nationals 5-4.
That was something Johnson acknowledged.
"I didn't just make it up or dream it up," Johnson said. "But I mean, there was conversations before the game. He was out there and I was talking to some of the guys and I said, 'How'd we let this guy get away?' I thought he pitched pretty good for us and I saw he's been a kind of invaluable setup man for Tampa Bay. One thing led to another and I got probably more information than I really needed. I don't know."