Houston will miss the playoffs for the ninth straight season of its existence and is guaranteed its worst record since going 6-10 in 2006, Kubiak's first season.
The Texans play Jacksonville (8-7) in their finale on Sunday, and speculation has intensified that not even an impressive victory over the Jaguars will be enough to save Kubiak and his staff.
Kubiak has deflected questions about his future for weeks, and he did it again on Monday, saying he's only focused on the finale.
"Nothing's changed for me," he said. "I wouldn't answer the question any differently. I'm concerned about trying to get ready to win a game."
Kubiak's contract runs through the 2012 season, and team owner Bob McNair offered a vote of confidence for his coach two weeks ago -- after the team rallied from 21 points down to tie, but eventually lose, a Monday night game to Baltimore.
Houston was then routed by Tennessee and collapsed in the second half against Denver, where Kubiak thrived as an offensive coordinator for 11 seasons under Mike Shanahan.
Kubiak said Monday that he's as shocked as anyone that the Texans' season unraveled so badly. The team started 4-2, overcoming the suspensions of linebacker Brian Cushing and left tackle Duane Brown for violating the NFL's policy on banned substances.
But when Kubiak looks back on the season, he'll lament the half-dozen games that got away since then. The Texans have led or been tied in the fourth quarter of seven of their past eight games, and lost all but one of those.
"Getting close doesn't matter. You've got to win those games," Kubiak said. "The key is to get yourself to play in games like that every week, and we're playing in them. We're not winning them. That's what's very disappointing. You have to learn to make those plays."
Kubiak said that the defense never recovered from the loss of Pro Bowl middle linebacker DeMeco Ryans, who ruptured his Achilles' tendon in the sixth game. The Texans have given up at least 24 points in each of their past eight losses.
"If I could change one thing, I'd like (Ryans) to be playing throughout the course of the season," Kubiak said. "That's a big, big miss. We lost our leader and our quarterback on defense the day we left the field 4-2. So that's been very, very difficult."
The Texans' defense ranks 29th overall and last against the pass, allowing 277 yards per game. Tebow threw for 308 yards on Sunday in his second career start.
Kubiak's decision to start rookie Kareem Jackson and second-year pro Glover Quin at cornerback has proven disastrous.
Houston has allowed 32 touchdown passes and 17 pass plays covering at least 40 yards, both league highs, and most of those defensive breakdowns have occurred in the fourth quarter.
"I don't think it's one mistake," Kubiak said. "I think there are things that happen through the course of a game that put you in those situations. But usually, in the fourth quarter, there are four, five or six plays that are the difference in the game, and you've got to make three or four of them. Obviously, we haven't been doing that."
With Sunday's loss, Kubiak's record slipped to 36-43 through five seasons. The Texans' progress has stalled after they went 9-7 last season, the franchise's first winning record.
"Words can't describe how I feel," Kubiak said. "We had a good team coming out of camp, a lot of reasons to be very optimistic. We had some issues early in the season, we weathered the storm very, very well.
"But the bottom line is we've lost five or six games that we easily could've won, and that's the difference between having a great season and having the season we're having right now."
Notes: Kubiak said WR Andre Johnson will sit out practice this week to nurse a sprained right ankle. Johnson skipped Sunday's game in Denver and is questionable for the finale. "If he tells me Friday that he feels good enough to play, then he's going to play," Kubiak said. "We'll have to wait and see how it goes." ... Kubiak said LB Darryl Sharpton will miss the Jacksonville game with a shoulder injury.