R.A. Dickey needs four more wins to become the franchise's first 20-game winner since Frank Viola in 1990.

Dickey picked up win No. 16 Saturday, when he limited Houston to one run on five hits and a walk in seven innings before telling Terry Collins he was losing steam with his pitch count at 86. The Mets eventually won, 3-1.

"He just said, 'I'm starting to lose it. The knuckleball is starting to come up,'" Collins said. "As I said the other day, you know, we think this guy is invincible. He's starting to get as run down as much as anybody else. He's pitched a lot of innings, probably a lot more than anybody else. So we've got to keep an eye on him."

Dickey said being tired was specific to this game, not really wearing down from the season. He added that he had a tough time with the knuckleball Saturday because of heavy air and difficulty gripping the baseball, even though he was throwing strikes.

"Today was particularly a difficult day because it was incredibly humid," he said. "I had worked out of some jams early on.

"You know, you're not going to go out there and feel great every single time. I had a pitch count that I should have thrown a complete game. But, the way I felt, it would have been selfish of me not to be honest about that. So when I came out after the seventh, I was honest with Terry about feeling a little bit run down today. And the way that we've been going, I wasn't going to go out there 'half-tanked.'

"I thought there were guys down there [in the bullpen] that could seal the deal. He could make whatever decision he wanted to after that, but we've got a good relationship. I've always been honest with him. And it worked out. He made the right moves and we won."

For now, Collins will use Dickey every fifth game -- not day. That would mean seven more starts for Dickey this season. If, toward the very end of the season, Dickey is within striking distance of 20 wins, the knuckleballer could be used every fifth day.

Dickey next starts Friday in Miami, on an extra day of rest, because Monday is a team off-day and the Mets will go straight through what's now a five-man rotation with Collin McHugh's demotion.

As for 20 wins, Dickey insisted he's taking it one game at a time.

"I'm just not in that place," he said.