How fast will these Eagles play?

They are the most mysterious team in the National Football League. What are the Philadelphia Eagles going to look like under first-year coach Chip Kelly? Exactly how fast is the offense going to play? What type of defense are the Eagles going to run? And who in the name of Donovan McNabb is going to be the starting quarterback?

We are about to find out.

NFL training camps open later this month, and teams begin the long march to try to become this season's version of the 2012 Baltimore Ravens. Every team is 0-0. Every team still has a dream.

But no team is more intriguing than the Eagles. After 14 seasons under Andy Reid, they have pivoted to an innovative offensive coach with zero NFL experience. Kelly was revolutionary at Oregon, where he led the Ducks to a 46-7 record in four seasons and introduced college football to his fast-paced, no-huddle spread offense. The Ducks redefined what it means to play fast. In 13 games last season, they ran 1,077 plays, a number that would have ranked seventh in the NFL's 16-game schedule. Oregon averaged 82.8 plays per game, a number that would have made New England, which led the NFL last season averaging 74.4 plays per game, look slow by comparison.

Can Kelly's up-tempo offense work in the NFL with a bunch of players who have never run it?

In the short term, the answer will be determined largely by which quarterback Kelly chooses as his starter. It is technically a five-man race. Kelly said throughout offseason practices that he doesn't have a depth chart -- only a seating chart -- but the race in training camp will be between Michael Vick and Nick Foles. Neither player significantly differentiated himself during the OTAs and minicamps.

Kelly wants to see how each player responds once the pads come on and, perhaps even more importantly, once the red jerseys come off. That means, for the first time in recent memory, the Eagles will have a full-fledged quarterback competition throughout training camp, and it might not get resolved until after the second preseason game at the earliest.

Although Kelly hasn't indicated when he will name a starter, the prevailing theory is that he will start one quarterback in the first preseason game and the other in the second. In May, Foles said he wouldn't be surprised if Kelly waited until the first week of the regular season to name a starter, because, Foles said, it is Chip Kelly, and no one really knows what he will do.

Kelly has said that the two most important criteria he is looking for are repetitive accuracy and decision-making. Given those guidelines, he could be in trouble. The Eagles were second to last in the NFL last season with a minus-24 turnover margin. Vick was largely to blame. Playing behind a patchwork offensive line that lost four starters to injury, Vick was often careless with the ball. He accounted for 15 of the team's 37 turnovers -- 10 interceptions and five fumbles -- but Vick was far from the only problem. In seven games, including the final six as the Eagles starter, Foles threw five interceptions and had three fumbles. In all, 11 Eagles lost fumbles; running backs LeSean McCoy and Bryce Brown had three apiece.

Neither quarterback was consistently accurate. In 10 starts, Vick completed 58.1 percent of his passes. Foles completed 60.8.

After Philadelphia's second-to-last practice of its full-squad, mandatory minicamp, Kelly laid out what he is going to look for to separate the quarterbacks.

"Who can move us the best, and who gets the football team up and down the field," Kelly said. "You know that's the most important thing. It doesn't have to be that he throws a prettier ball or all those things. There [are] a lot of different things. How do you manage a game? How do you secure the football? Are we not turning it over? Are we constantly moving in a positive direction? Are we getting into third-and-short and converting them? Things like that. It really is who moves the team the best is what we are looking for at the quarterbacks."

Asked how long it will take to answer those questions, Kelly said: "I don't know. We have to let it play itself out."

In the handful of spring practices that were open to the media, it was rare to see any quarterback throw a pass deeper than 10 yards in 11-on-11 drills. Vick and Foles split repetitions with the first-team offense equally. The tempo was fast, and the team employed a no-huddle system that included assistants calling in plays via elaborate hand signals from the sideline.

The consensus from those in attendance was that Foles had a slight edge in effectively getting the players lined up and then executing the plays. Vick has the stronger arm, but Kelly didn't sound like a coach who would become seduced by Vick's effortless throwing motion or his superior scrambling ability.

For the most part, both quarterbacks have handled the situation and the requisite barrage of questions about their competition with aplomb, although Vick told one local reporter that he wished Kelly would name a starter -- presumably him -- before training camp begins. That's understandable. In a market with dozens of reporters charting every throw, the scrutiny will be intense.

Naturally, Vick thinks he should be the starter. He has started 103 games in his 10-year NFL career, including 35 for the Eagles the past three seasons. At 33 years old, Vick might also be getting his last shot. He would like to make the most of it.

"I just want to see us win football games," Vick told me. "That's it. If you ask what's most important to me, it's that. That's why I'm here. To make up for what couldn't be accomplished the last two years. It's been tough, especially after the way we played in 2010 and thinking that we were good, and for it to not go right the last two years was very frustrating. The only thing we want to do is get out there and do it all over again."

And Foles wants his shot, too.

"I don't go to sleep at night sweating, wondering where I am" on the depth chart, Foles said. "What I can do is I can work hard, come out on the field, be a leader of these guys, execute the plays and make the guys around me better, and, at the end of the day, you know what? I did my job on the field. That's all I can do, and that's how I approach the game."

There are other questions surrounding the Eagles. For instance, how will Kelly employ his deep stable of tight ends, how much read-option will he run, if any, and will he have a vertical passing attack? On the defensive side, the Eagles appear to have switched to a 3-4 base defense, although Kelly refused to confirm that. Trent Cole, a defensive end his entire career, practiced as a linebacker, with Fletcher Cox and likely Cedric Thornton as the defensive ends and Isaac Sopoaga at nose tackle.

But the reason for the intrigue is Kelly's offense. Can it work in the NFL with his current crop of players, and can it work quickly? Philadelphia's schedule is unforgiving, beginning with a Monday night tilt with the Washington Redskins and followed by home games against the San Diego Chargers and the Kansas City Chiefs, which will mark Reid's return to Lincoln Financial Field. After that, the Eagles play at Denver, at the New York Giants and at the Tampa Bay Buccaneers before returning home to face the Dallas Cowboys and the Giants again.

The Eagles players want to win now. Many of the core players have endured a two-year stretch in which they've won only 12 games. They have bought in to what Kelly has sold them, but if the sledding is tough early, will they tune out a coach who has no NFL experience?

"I think he's just making everybody be accountable and buy in," wide receiver DeSean Jackson said. "I've been doing everything. I think my teammates have been doing everything. But we're grown men at the same time. It's the NFL, and I know he's brought a lot of stuff in from college, but at the same time, we all want to do better. The last couple of years have been kind of tough for us. Whatever it is, we have to figure it out on and off the field."

And that will make Philadelphia one of the most intriguing, must-see teams of the 2013 season.