Orton was injured when he took a big hit to the left side of his rib cage during the third quarter of last Sunday's 43-13 loss at Arizona. He managed to finish the game, but was so sore this week that he was unable to take any of the first-team practice repetitions over the past three days. It was the first time this season that Orton has missed any practice time.
Tebow, a former Heisman Trophy winner who led Florida to two national titles, took the bulk of the practice reps in Orton's place. Third-team quarterback Brady Quinn also got a significant amount of work with the first-team offense this week.
Interim coach Eric Studesville said he would wait until the weekend to make a final decision on his starting quarterback. While expressing confidence in Tebow's ability to step in, Studesville also pointedly declined to rule out Orton. Studesville said that if Orton got healthy in the next couple days, he had seen enough action this season to overcome his lack of practice and preparation.
"He's been out there every day, taking mental repetitions," Studesville said. "He knows this offense well _ he has been in there two years. But, at this point, we have not made any decisions."
However, Tebow has had a solid week of work and game plan for the Raiders was installed mostly with Tebow running the offense in practice.
"Tim has continued to develop," Studesville said. "He has the game plan. As a backup quarterback, you do not always get those reps. He has looked good getting those reps and we are confident if that is the situation that came to pass, he would be ready to go."
The weather could be an additional factor in Sunday's game in Oakland. Forecasts call for heavy rains over the weekend.
Tebow, who hasn't played more than two consecutive snaps in a game this season -- and usually sees action in specialized situations -- wasn't fazed by the prospect of sloppy conditions.
"I've had some of my better performances in bad weather," Tebow said.
In other injury-related developments, the Broncos ruled out safety Brian Dawkins (knee), kicker Matt Prater (groin) and wide receiver Demaryius Thomas (ankle) for Sunday's game.
Steven Hauschka will kick in Prater's pace for the second consecutive game. He made two of three field goals last week in Arizona. Dawkins will miss his third consecutive game since injuring his knee Nov. 28 against St. Louis. Thomas has been sidelined since twisting his ankle Nov. 22 against San Diego.
More from NFL.com: