In theory, the defense-laden Sabres can keep all nine of their NHL defensemen in Buffalo. The roster limit is 23, so they can field 12 forwards, two goaltenders and nine blue-liners.

That, however, would not give Relativity or Big Bang a run for best theory ever. It would waste talent, assets and the patience of players and coaches.

So, with the season opening in just five days, the Sabres’ brain trust has significant decisions to make. It’s likely one was made for them Monday.

Prior to the intrasquad scrimmage that brought 10,175 fans to First Niagara Center, the Sabres lost minor-league defenseman Joe Finley on waivers. The New York Islanders claimed the hulking 6-foot-8, 249-pounder, who had one goal, five points and 81 penalty minutes in 36 games with Rochester.

“It was disappointing,” Sabres General Manager Darcy Regier said after the 1-1 scrimmage tie. “While I was surprised, there’s an element to Joe’s game that I understand why a team might have an interest in him.”

Finley appeared in five games with Buffalo last season but played less than eight minutes per outing. T.J. Brennan, meanwhile, is competing for significant minutes with the Sabres. After leading the Amerks with 14 goals and 35 points in 36 games, he arrived in Buffalo’s camp Sunday to skate against the other eight blue-liners who are eager for playing time.

Like Finley, Brennan would need to clear waivers to return to Rochester. If a player with a limited NHL role like Finley can get claimed, it’s a certainty the offensively gifted Brennan would draw suitors. Any thoughts the Sabres had about sneaking him back to the minors to ease their logjam are probably gone. The same goes for the other NHL-caliber blue-liners.

“You’d prefer trade versus waivers for the individual,” Regier said. “If the player can’t play here, you’d hope that they’d have an opportunity elsewhere and you can get something in return for that as well.”

The Sabres normally dress six defensemen. They’ve had eight on the roster at various times through the years, but coach Lindy Ruff has expressed his disdain for the practice.

At least one blue-liner has to go. The question is who.

“What’s obvious is we have nine guys that can play,” Ruff said. “It’s a decision that we’re going to have to make when it comes down to our first game on who those six guys are going to be.”

Tyler Myers and Christian Ehrhoff, by virtue of their status and contracts, are not going anywhere. Here’s a look at the remaining defensemen.

• Jordan Leopold: He has 23 goals and 36 assists over the last two seasons, making him one of the Sabres’ most consistent defensemen. He also makes a reasonable $3 million. But he’s in the final year of his contract and could be lost for nothing at the end of the season.

• Robyn Regehr: Acquired prior to last season, Regehr was viewed as the missing, physical, stay-at-home piece of the Sabres’ puzzle. He was one of the dominant players in the scrimmage, but he finished last season getting ripped by Ruff for allowing a goal in Philadelphia that ended Buffalo’s playoff hopes. (Ruff later apologized.) Regehr, 32, also is in the last year of his contract, which pays $4 million.

• Andrej Sekera: The 26-year-old is in the second season of a contract that averages $2.75 million. He’s blessed with offensive skills, especially skating. He underachieved with three goals and 13 points in 69 games last year.

• Alexander Sulzer: Acquired at the trade deadline as a throw-in to the Cody Hodgson deal, he blossomed in Buffalo and was arguably its best defender down the stretch. He had three goals and eight points in 15 games. The 28-year-old was re-signed to a one-year, $725,000 deal.

• Brennan: He had one goal and no assists in 11 games with Buffalo last year. The 23-year-old makes $550,000.

• Mike Weber: A physical defenseman, Weber has had his ups and downs during four seasons with Buffalo. There have been times he’s been a vital piece to the blue line, and others when he can’t crack the lineup. He makes $900,000.

• Adam Pardy: The biggest unknown among Buffalo’s defenders. Acquired as part of the trade that brought Steve Ott to town over the summer, Pardy had three assists in 36 games with Dallas last season. He played 30 games for the Stars the previous year after 57- and 60-game campaigns with Calgary. He’s in the final year of a contract that pays $2 million.

There’s no easy fix to get to six. It appears trades or nail-biting while sending someone through waivers is imminent. The Sabres need to be at the roster limit at 5 p.m. Friday, so the final time to place players on the 24-hour waiver wire is noon Thursday.

“There’ll be a lot more players on waivers Thursday afternoon,” Regier said, “and there’ll be competition in the waiver system.”