"This was the right idea at the wrong time," Seinfeld said while promoting his new reality show, "The Marriage Ref," in Los Angeles Sunday. "I'm proud that NBC had the guts to try something."
Seinfeld also said O'Brien will emerge from the wreckage unscathed.
"What did the network do to him?" Seinfeld asked. "I don't think anyone's preventing people from watching Conan. Once they give you the cameras, it's on you. I can't blame NBC for having to move things around. I hope Conan stays, I think he's terrific. But there's no rules in show business, there's no refs."
It remains to be seen if O'Brien will stay with the network that made him a star of if he'll fly the coop. He's reportedly exploring his options with Fox, but Monday, Fox entertainment president Kevin Reilly told reporters that his network is waiting for O'Brien to determine his own fate with NBC before making an offer.
"I love Conan personally and professionally. But right now, he has to make a decision," Reilly said.
Amid sinking ratings and worried affiliates, NBC announced Sunday that the Jay Leno primetime experiment will end Feb. 12.
NBC confirmed Sunday that it will yank the comic's 10 p.m. nightly hour once the Winter Olympics begin, and it hopes he will accept a half-hour version of his show at his old time -- 11:35 p.m. -- instead.
"While it was performing at acceptable levels for the network, it did not meet our affiliates' needs and we realized we had to make a change," NBC Universal Television Entertainment Chairman Jeff Gaspin said at the NBC winter press tour in Pasadena, Calif., Sunday.
"What happened starting in November [was] the affiliates called, saying, 'Wow, wow, our local news is being affected more than we expected,'" Gaspin said.
NBC has spoken to Leno, Conan O'Brien and Jimmy Fallon about moving their shows to later start times, Gaspin said. Under the proposal, O'Brien, the man who replaced Leno as host of "The Tonight Show," would move to 12:05 a.m., and Fallon to 1:05 a.m.
"My goal right now is to keep Jay, Conan and Jimmy as part of our late-night lineup," Gaspin said. "As much as I would like to tell you we have a done deal, we know that's not true. The talks are still ongoing."
Last week, amid a firestorm of speculation that NBC might can O'Brien altogether, the network released a statement this week declaring its loyalty to the late-night comic.
"We remain committed to keeping Conan O'Brien on NBC," the network said in a statement Thursday evening. "He is a valued part of our late-night lineup, as he has been for more than 16 years, and is one of the most respected entertainers on television."
ABC News' David Alpert and Brian Rooney contributed to this report.