Sam Bradford never finished better than 18th in the NFL in completion percentage in four seasons with the Rams, and yet, when Chip Kelly was asked what separated the quarterback from Nick Foles, he said "overall accuracy."

The numbers don't support the Eagles coach's claim. Bradford's 58.6 career completion percentage is three points lower than Foles' 61.6 mark. But numbers don't always tell the full story, and it's clear that Kelly has calculated the difference he expects his offense will have on the success of Bradford following this month's trade with St. Louis.

While Foles' completion percentage playing in Kelly's offense (62.4) was greater than it was during his rookie season under Andy Reid (60.8), the bump Mark Sanchez got last season with the Eagles (64.1) after a large sample of games with the New York Jets (55.1) was even more significant.

Kelly, though, downplayed the idea that Bradford or any quarterback would improve his accuracy throwing in his system.

"I can put some players in there, and they're not going to complete a pass. It's still personnel driven," Kelly said last week during the NFL owners meetings. "That whole, 'It's the system, It's not the system' - it's still about the players, and putting them in positions where you can read their strengths and read their weaknesses and put them in position to make plays."

But does Kelly put his players in positions to succeed better than most offensive coaches? Not only did Foles and Sanchez thrive, but running back LeSean McCoy and wide receivers Jeremy Maclin and DeSean Jackson had the best statistical seasons of their careers under Kelly.

Any evaluation of Bradford has to include his injury-riddled past. He has missed 31 games over the last four seasons and hasn't taken a meaningful snap since October 2013 after tearing the anterior cruciate ligament in his left knee twice in 10 months. Kelly's gamble hinges on the 27-year-old quarterback's health.

But a projection with the Eagles must also take into account Bradford's first four seasons with three offensive coordinators, the lack of a single Pro Bowl receiver, and an offensive line that couldn't consistently protect him. Sanchez dealt with the same obstacles (aside from the offensive line) in New York.

Not only did Sanchez's accuracy improve last season, but his yards per pass attempt jumped from a 6.7 average with the Jets to 7.8 with the Eagles. Bradford averaged only 6.3 yards per throw with the Rams.

He had a solid rookie season with Pat Shurmur calling the plays, but the West Coast offense uses short passes, and Bradford didn't have receivers who could consistently get yards after the catch. Josh McDaniels took over as offensive coordinator after Shurmur left for the Browns, but the 2011 season was a disaster that ended with coach Steve Spagnuolo's firing.

New coach Jeff Fisher brought in Brian Schottenheimer, but the coordinator turned Bradford into a Check-down Charlie rather than take advantage of his arm strength. Kelly said he watched every throw Bradford made in the NFL but focused on his skill set without knowing what his responsibilities were on any given play.

"You don't know what he's asked to do," Kelly said. "Like I don't know what the play call is on the third throw of the game, or what his progression was from one to two to three, or was he told to throw it there no matter what?"

But Kelly knew the decisions Foles had made in his offense, and there were many times last season when he missed open receivers. The same could be said of Sanchez, but he wasn't brought back to start.

"We've got guys open, and we didn't put the ball on them in certain situations," Kelly said.

Both quarterbacks were turnover-prone in 2014. Foles had 13 turnovers in eight games, while Sanchez had 14 in nine games. Foles' interception rate (3.2) was 28th in the league, and Sanchez's (3.6) was 31st. Kelly's offense might have improved Sanchez's accuracy, but the quarterback's interception rate was essentially the same as it was with the Jets (3.7).

Bradford was much more careful with his throws. His 2.2 interception rate is third to only Aaron Rodgers and Tom Brady among active quarterbacks with more than 1,500 pass attempts. If Bradford continues to make the right decisions, Kelly's offense, which simplifies pre-snap defensive reads, should utilize his quick mind and quick trigger.

"From what I've seen it looks like everything goes through the quarterback," Bradford said earlier this month. "What do you like? How do you see things? And then they're going to tailor it from there. They're never going to put you in a bad situation where you have nowhere to go with the ball, and you're standing back there holding on to the ball for five seconds."

Many of Bradford's struggles stemmed from his inability to navigate pressure in the pocket. He fumbled 27 times and was sacked 120 times in 49 games. He is not fleet of foot and now has a twice-injured knee.

Kelly pretty much abandoned his productive zone-read running plays last season with the immobile Foles and Sanchez. He said he wouldn't use the option much with Bradford either. Many still believe Kelly, ideally, wants a dual-threat quarterback such as Marcus Mariota.

While that hope remains for some, the flame is flickering. Bradford has been omnipresent at the NovaCare Complex since the trade and has already begun learning the offense with center Jason Kelce.

"I think he's a guy that comes off very cerebral, very smart, very quick," Kelce said. "He's had a lot of bad luck in his career as far as injuries are concerned. And as far as - and I don't want to throw any offensive lines under the bus - I think he's much better now with us.

"I think he has a good chance to be very successful in this offense."

Improving Their Aim

Can Chip Kelly's offense make a QB more accurate? Here are the completion percentages for Nick Foles (9) and Mark Sanchez with Kelly and before they played for him.

   Before   With   

Kelly   Kelly

Foles   60.8   61.9

Sanchez   55.1   64.1

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jmclane@phillynews.com

@Jeff_McLane