As Chip Kelly noted, if the Eagles played their regular-season opener Thursday, it would have been "illegal" or something like that. His underlying message: Just because Sam Bradford's left knee doesn't appear remotely close to 100 percent healthy on May 28 doesn't mean that Mark Sanchez will be the starting quarterback 109 days later.

But with each passing day that Bradford is not completely back from tearing his anterior cruciate ligament, the specter of Sanchez under center on Sept. 14 in Atlanta becomes more and more of a reality.

Kelly said Bradford's recovery was on schedule. Many NFL players return from ACL injuries in the nine months since Bradford tore his. But not many had to endure a second ACL tear in the same knee only 10 months after the first.

So the Eagles will proceed cautiously.

Earlier this month Bradford practiced one week only to sit out practice the next. He said it wasn't a setback and that "they" (Coaches? Doctors? Trainers?) just wanted to push his knee to see how it responded. Not practicing suggests that it didn't respond well.

Kelly isn't panicking.

"The research our doctors have given us in terms of the guys coming off those injuries, in terms of their recovery rate, is 90 percent," Kelly said, "so we feel real confident in that."

Bradford wore a large brace around his left knee Thursday. He was the only player who did not participate in conditioning warm-ups. He threw only during individual drills. He jogged without a limp in between the drills, but when he walked off the field after practice he was clearly favoring his left leg.

Maybe it was the heavy brace. Maybe it wasn't.

But if Bradford isn't participating in seven-on-seven drills next week, as Kelly said he expected him to, or if he isn't taking 11-on-11 repetitions by minicamp in mid-June, or if he isn't ready by training camp in early August, then how ready will he be learning a new offense in a short time? More important, where will he be mentally?

One-hundred-eight days and counting down.

Which brings the Eagles to Sanchez. He agreed to a two-year contract days before Kelly traded Nick Foles and a second-round draft pick in 2016 to the Rams for Bradford. Sanchez didn't sign the deal until after the trade. He couldn't have been pleased that his competition had changed.

"Were there other opportunities? Absolutely," Sanchez said when asked about free-agent negotiations he had with other teams. "Did they look potentially good, better, similar, maybe worse? Potentially, yeah. There was some stuff out there. But when I factored it all in, I felt this was the best spot for me."

Sanchez likely thought he could beat Foles out. He's probably confident enough to believe he can supplant Bradford, too, but the Eagles gave up an awful lot to get the former No. 1 draft pick and will pay him nearly $13 million this season. If he's healthy, Bradford has to start.

Sanchez said he didn't consider that an obstacle.

"You act like you're the starter, and that's the only way I know how to play," Sanchez said. "As soon as you start thinking and counting reps, or 'I wonder if this guy is going to be healthy,' then you're already beat."

Kelly said that there would be an open competition, but will it be a legitimate one, with Bradford and Sanchez splitting snaps as Michael Vick and Nick Foles did two years ago? If so, it could be closer than their pasts would suggest.

Bradford, when healthy, has better tools. When he did throw Thursday, the ball zipped out effortlessly. But how will the knee affect his performance and his mental state? If Sanchez is clearly better, could Kelly afford to nullify his big offseason acquisition and go with the better man?

The Bradford-for-Foles trade would look foolish, but Kelly doesn't care much about perceptions, or at least that's what he said Thursday.

Sanchez is far removed from last year's organized team activities, when he was still not 100 percent recovered from shoulder surgery and it showed in many of his passes. He improved dramatically over the next several months, and when it came time to come off the bench for the injured Foles, he rallied the Eagles to victory over the Texans.

But his next eight starts were marked by inconsistency. He was hardly the sole contributor in the Eagles' three-game December slide, but the turnover problems he had with the New York Jets resurfaced.

"I felt I left some opportunities out there," Sanchez said.

But he completed 64.1 percent of his passes - an increase of 9 percent over his career average. He ran the up-tempo part of Kelly's offense better than either Foles or Vick. And he conceded now that his shoulder still wasn't all the way back.

"This is definitely the best I've felt," Sanchez said.

The same can't be said for Bradford. The starting spot is his to lose, but he can't win it until he starts practicing full time.

One-hundred-eight days and counting down.

@Jeff_McLane