Because of the unpredictable nature of nerve injuries, the Arizona Cardinals are not presently considering placing quarterback Carson Palmer on season-ending injured reserve or IR-designated to return, according to a league source.

With Carson Palmer's status for Sunday's game in the air, Drew Stanton stands to make his third straight start for the Cardinals. Brad Penner/USA TODAY Sports

Palmer returned to the team Thursday after suffering a setback while throwing late last week that prompted him to leave for a second opinion on the damaged nerve in his right shoulder. The injury was suffered during a Week 1 win against the San Diego Chargers and forced Palmer to miss the past two games for the undefeated Cardinals.

His status for Sunday's game at Denver remains undetermined, although it seems unlikely the veteran quarterback will achieve his goal of returning this week. Palmer went to the facility for treatment and rehab daily, describing it as one of the most important weeks of his career.

"It's still week to week," Cardinals coach Bruce Arians said Wednesday when asked if there was long-term concern about Palmer's status. "If we thought it was long term, we could always put him on IR with a chance to return, but we're not even close to that yet."

Arians called Palmer doubtful for Thursday's practice but said if the 34-year-old returned by Friday there was a chance he can start this weekend. If Palmer doesn't practice Friday, he won't start but could be available as Arizona's backup, Arians added, meaning Drew Stanton would get his third straight start.

"We need to see two good days or a day and a half of his full-speed delivery and not a soft toss," Arians said. "He's got to be back to full tilt."

The team has until Week 8 to decide if Palmer would go on IR-designated to return. At Week 8 or later, he would have to miss the rest of the regular season.

ESPN.com Cardinals reporter Josh Weinfuss contributed to this report.