Johnson was injured late in the third quarter of Sunday's game at Reliant Stadium against the Atlanta Falcons. He had an MRI on Monday morning.
"We're very fortunate," Kubiak said. "I'll tell you today he's day-to-day. I probably can give you a better answer once we give him a couple days here and get to Wednesday, but we do expect him back, and hopefully sooner than later. To answer today, we feel very fortunate."
Johnson missed six games earlier this season with an injury to his right hamstring. After Sunday's game, Johnson said the injury was "nothing near" what he felt in Week 4 against Pittsburgh, and Texans owner Bob McNair said he hoped Johnson would be able to return in a couple of weeks.Hartmann, an undrafted free agent out of Central Michigan, was hurt in the fourth quarter while running downfield to cover a punt. He was not touched on the play.
"It's very unfortunate for him," Kubiak said. "He was really having a good year, a young man who was doing a god job, so we'll have to replace him here in the next few days."
The Texans will work out a couple of punters and sign one tomorrow. Kubiak said it's possible they sign Matt Turk, a free agent who punted for the Texans from 2007-10 and was the holder for kicker
Hartmann will finish the year with a 44.4-yard punting average, a new franchise record. He also set team records for longest punt (69 yards) and most touchbacks on kickoffs (23). He ranks 21st in the NFL in punting average and net punting average (37.8) and 16th in average yards per kickoff (65.7).
Kubiak said linebacker
Kubiak doesn't think the field at Reliant Stadium is at issue with any of the injuries. The field is comprised of square trays of natural grass that are eight-by-eight feet and transported to the stadium from a nearby location. A high school game was played at Reliant on Saturday evening.
"I think our field looked excellent to me yesterday," Kubiak said. "It’s obviously a field that's put together different than most fields, but they do a great job of rolling that thing and putting it together.
"What we saw took place on the film yesterday, especially with Brett, had nothing to do with any part of the field or anything. He just got out of control and stuck his foot in the ground. That’s happened on many fields, not just our field. So, I don’t see that."