Concerned Harvey is doing too much, too fast in his return from Tommy John surgery, Collins implored the right-hander not to jeopardize his 2015 season by rushing back from the Oct. 22, 2013, procedure.
Collins added that Harvey will not be pitching in a game this season.
The manager also asked Harvey not do to radio interviews during Mets games.
Harvey, rehabbing in Port St. Lucie, Florida, threw a 27-pitch bullpen session Wednesday. He did a radio interview that night with ESPN New York 98.7 while the Mets game against the Washington Nationals was in progress, which caught his manager off-guard when questioned about it postgame.
Despite organization pronouncements that it is unwise to pitch in a game this season, Harvey reiterated in the radio interview that logging innings in 2014 remains his aim.
"I felt like I was easily throwing into the low- to mid-90s, with pretty much no effort," Harvey told ESPN New York 98.7 on Wednesday, referring to that morning's mound work. "I know there's a process, but as a competitor I want to get out there as soon as possible."
On Thursday, Collins acknowledged the same personality that makes Harvey a force on the mound also makes it difficult to contain him now.
"No. 1, he's a tremendous competitor," Collins said. "That being said, he's a bulldog at the same time. There's no backing down with Matt Harvey -- for anything. He was bound and determined to get ready. We slowed him down. It frustrated him to the max. He's feeling good."
The Mets have tried to use right-hander Jeremy Hefner's current predicament as a cautionary tale for Harvey. Hefner, who underwent Tommy John surgery two months before Harvey, had a major setback last week while pitching in a minor league game and likely needs to repeat the surgery.
"He wants to try to get back here to help," Collins said about Harvey. "And I explained to him, 'I understand that. But ... you have got to understand the big picture. And the big picture is 2015. So back off.'
"Now, unless I'm standing next to him, I can't control it. You guys think I can. I can't; it's impossible. This guy will hire somebody to go throw with him. That's the way he is. That's just how he is. I just said, 'You've got to be smart about this. And, by the way, stop doing radio shows during the ballgame telling everybody you're throwing 95 mph. That isn't going to help us up here.'
"He gets it. He said, 'Yeah, I just wanted to let them know I'm fine.' I said, 'Yeah, but there's a phraseology you could use to say, "Hey, look, I'm doing fine and I'm making progress."'"
Collins nonetheless believes Harvey will contribute in 2015 without issue.
"I'm not worried about Matt. He's going to be fine. I know he's going to be fine," Collins said. "He's going to get through the process. He's not going to pitch this year. I'm settled with that. He's settled with that. And I've just told him you've got to take a look at the big picture and you've got to be careful what you're doing and what you're saying, because you have to be here next year. We can't afford to have what happened to Jeremy happen to you.
"Now, does he get it? You'd have to ask him. I mean, I can't answer that for him. I just trust him. I just trust him that he gets it. So we'll see."