The Colorado catcher's throwing error in the ninth inning let the Mets tie it. But once again, New York let a scoring opportunity pass, leaving runners on second and third in the top of the 10th.
Ianetta led off the bottom half with a home run to give Colorado a 6-5 win Wednesday night.
"For him it's great because he's a guy that works so hard," said Ryan Spilborghs, who also homered. "For him to see results like that, it's great."
In the ninth, Gary Matthews Jr. began with a single off closer Franklin Morales, stole second and took third when Iannetta's throw went into center. After Jose Reyes struck out, Luis Castillo scored Matthews with a sacrifice fly.
"I tried to put it around the bag and I threw it short," Iannetta said. "Nine out of 10 times the middle infielders get that, that's why I don't mind bouncing the ball to second base.
"I showed emotion but at soon it was over I let it go. It's part of being a catcher. It's tough at times."
It's been tough at the plate for the catcher, too. Iannetta entered the game 1 for 12 but broke out of the early-season slump with three hits. He capped the night when he sent a pitch from Jenrry Mejia (0-1) into the centerfield bleachers to give the Rockies their third straight win and send the Mets to their fourth loss in a row.
"You're going to go through 12 at-bats over the course of the year where you're not going to have success," he said. "My biggest thing was try not to make too much of it. I was just looking for something over the plate and put a good swing on it."
"I didn't mind that matchup at all," said manager Jerry Manuel, whose Mets are 12 for 72 (.167) with runners in scoring position.
"We haven't done well hitting with runners in scoring position," Manuel said. "We have to do better in that area."
New York cut the lead to 5-4 on Rod Barajas' two-out RBI single in the eighth.
The Mets took a 3-1 lead in the third when Castillo singled with one out and Wright hit his third homer of the season off Aaron Cook.
Colorado answered in the bottom of the third off Mets starter Jonathan Niese. Todd Helton doubled with one out, Troy Tulowitzki walked and Spilborghs drove Niese's 2-2 fastball over the centerfield wall to make it 4-3.
The Rockies made it 5-3 in the fourth when Cook scored on Dexter Fowler's single. He also led off the sixth with a double but was stranded.
Cook was in line for his first win of the season after giving up three runs on four hits and striking out four in six innings.
"I didn't have a great sinker today," Cook said. "I just tried to keep the team in the game as long as I could."
Niese allowed five runs on nine hits, struck out two and walked one in five innings.
The Mets scored first when Francoeur hit Cook's first pitch in the top of the second down the left-field line for his third home run of the season. The Rockies tied it in the bottom half of the inning on Clint Barmes' one-out double that scored Ian Stewart from second base.
"These are frustrating loses," Wright said. "We fought back, didn't get the hit when we needed it and it's another loss."
Francoeur has hit safely in all eight of New York's games this season and has seven extra-base hits. ... Colorado OF Brad Hawpe didn't start because of tightness in his left thigh but pinch-hit in the eighth. He could return to the starting lineup Friday in Atlanta. ... Rockies OF Carlos Gonzalez (left hamstring tightness) missed his second straight game. ... The Mets have not allowed an unearned run this season.