NEW YORK -- As promised, Mets manager Terry Collins rested second baseman Daniel Murphy in Friday's series opener against the Astros, starting Justin Turner in what should be a two-day respite.

Concerned about Murphy's energy level and eager to give Turner an uninterrupted string of at-bats, Collins said that the switch will be in effect on Saturday, as well.

"When you look at his last two years, one of them he didn't play at all, hardly," Collins said of Murphy. "The other one, last year, he got hurt and missed quite a bit of time. He's playing a new position. So I think not just physically, but mentally, the fact that he's at a new spot has worn him down a little bit because he plays every day as hard as anyone I've ever been around. He loves to play. He's a workaholic. I just think it's time for him to take a couple days."

Though Murphy told his manager that he felt well enough to play this weekend, the symptoms of fatigue were obvious to Collins. Since hitting his last home run on Aug. 8, Murphy has batted .122 with a .170 on-base percentage. Turner, meanwhile, has not started back-to-back games since June 20-22, making the move as much about giving him at-bats as it was about resting Murphy.

Mets option McHugh to make room for Hefner

NEW YORK -- Collin McHugh's parting gift was a handshake from Johan Santana, as the two passed each other in the Citi Field dugout on Friday afternoon. Santana was heading out to the field to stretch. McHugh was heading back to the Minors.

Despite McHugh's dominant big league debut on Thursday, the Mets optioned him to Triple-A Buffalo a day later to make room for Jeremy Hefner, who is coming off paternity leave.

Such can be the injustice of baseball, manager Terry Collins explained.

"As I explained to him, this has happened many times before -- other places, not just today," Collins said, a day after McHugh struck out nine over seven scoreless innings. "There's no sense in having him sit here when we would have had to send somebody out to leave him here. I just said, 'Go out. Get a start in. And then you'll be back and fit right back in the rotation.'"

Collins' justification is that McHugh would not have pitched again until Aug. 30 anyway, and he will be eligible to return to the Mets on Sept. 3. So rather than have him sit idle for a week in the club's six-man rotation, the Mets sent McHugh to Buffalo for what should be one last Minor League start. Then he will slot back into the big league rotation in September.

In the interim, the Mets will revert to a five-man starting staff for the remainder of August. With an off-day Monday, all Mets starters will receive an extra day of rest regardless, accomplishing what the team hoped to out of its six-man rotation.

That starting staff could grow crowded when rosters expand in September, with the Mets also hoping to give Jenrry Mejia a few looks down the stretch. But Matt Harvey is on a strict innings limit and Chris Young could benefit from additional rest, meaning starting assignments should be available for the taking.

As for McHugh, the rookie celebrated his successful debut with his parents, wife and siblings in New York, going to dinner and exploring the city to conclude his two-day stay.

"We had a fun night," McHugh said. "We went out and had a good dinner and saw some of the great city, and just had a really good time."

Worth noting

• Hefner returned to New York on Friday, two days after his wife, Sarah, gave birth to a healthy baby girl named Jaylee. Hefner, who was away from the team for three days, is scheduled to start Sunday.

• The Mets wore their popular blue "Los Mets" jerseys for Merengue Night on Friday, as part of an exception from Major League guidelines that include restrictions on alternate jerseys. But the Mets will be eligible to incorporate blue jerseys into their regular rotation beginning next season.