Updated OCT 03, 2014 10:22p ET  METARIE, La. — The New Orleans Saints' struggling defense was dealt a significant setback Friday when the team learned that three-time Pro Bowl safety Jairus Byrd will miss the rest of the season with a knee injury.  Byrd injured his lateral meniscus during practice on Thursday, coach Sean Payton said, and had surgery on Friday — two days before New Orleans' home game against Tampa Bay.  ''It was a play where he just kind of turned to catch a ball down the field and kind of tweaked his knee and got up, and obviously, it was more significant than that,'' Payton said. ''The good news is the repair went well, and it's something that, with the right rehab and treatment, there should be no carry-over effect'' next season.  Reserve safety Rafael Bush, a regular in New Orleans' defensive backfield, has been promoted to Byrd's starting spot, Payton said.  Byrd's father, Gill, is a cornerbacks coach with the Buccaneers. So while Payton generally avoids giving away significant personnel changes to opponents in the days leading up to a game, he made an exception in this case.  ''It was important that he let his dad know and that was more important, obviously, than the opponent not knowing,'' Payton said. ''As a father, I would want to know.''  The Saints signed Byrd to a six-year, $54 million contract this past offseason, when the safety became a free agent after spending his first five NFL seasons in Buffalo. Byrd intercepted 22 passes during his first five years in the league, more than any safety during that span.  In four starts this season, Byrd had yet to intercept a pass, but created a turnover with a forced fumble in the season opener at Atlanta.  ''It's a big loss. Byrd's not just a great player, he's a great teammate. It's going to be unfortunate to not have him around as much,'' fellow starting safety Kenny Vaccaro said.  Still, the defense was struggling even with Byrd on the field, ranking 29th with 396 yards allowed per game. And Vaccaro noted that in that sense, the unit has to improve, with or without one of its top defensive backs.  ''The way we were playing, we had so many different issues, we had so many things to fix, that it's like, `All right, we're going to have to overcome all these other things anyway,''' Vaccaro said. ''So it's a loss, but you get what I'm saying. We were playing so bad across the board that it can't get worse, I don't care who you lose. ... You can plug anybody in and play better (as a unit) than how we've been playing.''  Bush said he expected to be ready for the elevated role, just as he was around this time last season, when he had to step in for then-injured safety Roman Harper and proved himself valuable enough to coordinator Rob Ryan's unit that the Saints matched a restricted free-agent tender that Bush had received from Atlanta.  ''It's a profession and everybody has to know their job inside and out and everybody has to understand that in this game, it's 100 percent chance of being injured, so you could be up just like that,'' Bush said. ''You just want to make sure you prepare yourself well enough to where, if you go out there, your teammates can trust you, you can execute your plays and be able to make sure there's not any drop-off.''  Ryan, meanwhile, rejected the notion that an injury to one of his top players necessarily meant that his unit would regress even further as a whole.  ''We're coming together as a group. I know we didn't play well last week. We're ready to go,'' Ryan said. ''We're excited about this challenge. We're looking forward to this game.''  ''With our secondary being as multiple as it is, we have guys in different spots playing a lot. We have a Rafael Bush who's a fantastic football player,'' Ryan said. ''We're going to be fine. It's a big loss. He's such a great person and great player, but we have an excellent football player there.''  NOTES: In addition to Byrd, the Saints have ruled out RB Mark Ingram (hand) and FB Erik Lorig (ankle). However, S Marcus Ball (hamstring), who has not yet played this season, was listed as probable. ... Byrd, a sure-handed veteran, also had been used as a punt returner in likely fair-catch situations as opposing punters tried to pin the Saints inside their own 20. Now rookie receiver Brandin Cooks, who has been lining up deep for more returnable punts, is now expected to be the primary punt returner regardless of field position, special teams coordinator Greg McMahon said.
The most prized free agent of this past year's class will watch the rest of the season from the sideline.