He'll be out at least four weeks, but it really depends on how the 29-year-old Czech native responds to treatment on his strained medial collateral ligament. He's never had an injury on the left knee.
Signed July 1 to a US$20-million, four-year deal as one of Toronto's key off-season additions, this is the last thing Kubina wanted early in the season as he tried to prove to fans and the media he's worth the big money.
"It is frustrating, but there's nothing I can do," said the former Tampa blue-liner.
He also dismissed the theory that his injury sustained in Monday's game against Florida had to do with bad ice at the Air Canada Centre.
"Definitely not, that was not an ice issue," stressed Kubina. "It was a collision in front of the net with (Todd) Bertuzzi. He fell on my left knee and pushed my knee inside. I felt a lot of pain right away and I couldn't get up.
"It was, I'd say, bad luck, just a collision in front of the net. Not an ice issue at all."
He's the most significant in a long line of injured Toronto defencemen, joining Andrew Wozniewski (shoulder), Carlo Colaiacovo (head), Staffan Kronwall (ankle) and Brenden Bell (foot).
"Like four guys are out right now," said Kubina. "Sometimes you go through half a season without injuries and sometimes (you have) a lot of guys going down."
Bell is nearing a return. He skated alone with assistant coach Keith Acton before practice Wednesday and later joined the rest of the team for their skate.
"I think my conditioning needs a little bit but I'd be willing to get into a game," said Bell. "There's a little ways to go but I'm pretty close. I'm ready to go whenever they want me."
Saturday's game against Calgary is a more likely return date for Bell. Tough guy Wade Belak, who started the season at forward, was back on defence in practice with Jay Harrison as his partner and would likely be there for Thursday's game at New Jersey.
"I'm comfortable with Belak on the blue-line," said head coach Paul Maurice, who doesn't want to rush Bell back unless team doctors say it's OK.
"First, Brendan is still injured until someone tells me different," added Maurice. "No player is coming back earlier than he is ready because we have players with the (AHL) Marlies."
Meanwhile, Maurice announced that backup J.S. Aubin would get his first start of the season at New Jersey.
"I think he a good goaltender and I don't think these guys can sit out that long and stay sharp," said Maurice. "He had a very good camp and I think the timing is right."
Maurice will also stick with a late-game line change he made Monday night. The coach replaced Alexei Ponikarovsky with winger Darcy Tucker on the top line with Mats Sundin and Kyle Wellwood.
"It has absolutely nothing to do with Darcy Tucker," said Maurice. "It got to do with Alexei Ponikarovsky. When he and Stajan and O'Neill get the second half of that power play they also get some time together five on five. I really like the way they played together.
"So I didn't think I was losing anything by putting Darcy with Mats. It makes the bench easier to run."
Tucker was unfazed by the change.
"It doesn't really matter," said the 31-year-old veteran, who is off to fast start with four points (3-1) in four games. "There's a lot of good players on this team. I'm happy to play anywhere. Maybe when I was younger it would have been a big deal."