Chip Kelly's puzzles getting more complex

Above all, Chip Kelly enjoys fitting together the puzzle pieces that form a football team, but the process of doing so sometimes seems to just create more puzzles. He might have the solution to all of them, but the rest of us will just have to wait and find out. Chip isn't really saying.

There were a number of puzzles to consider on Wednesday as the Eagles bounded through the shimmering heat at the NovaCare Complex for another day of training camp with the start of the regular season just one month away.

On the offensive line, the very real question of who will play either of the guard positions was still being asked while Evan Mathis continued his lonely workouts in Arizona. You like Julian Vandervelde? He's getting reps, but then so are Andrew Gardner, Matt Tobin, Allen Barbre, and John Moffitt.

At the outside linebacker position, because of the earlier injury to Travis Long, every snap taken by former first-round pick Marcus Smith was scrutinized while Trent Cole spent his day at the Indianapolis Colts training camp (along with Todd Herremans, another of the missing guards).

And then there is the defensive backfield, which is deeper than ever, according to Kelly, but like a deep lake, it is also a lot murkier. The Eagles traded away slot cornerback Brandon Boykin for a fifth-round draft pick (a conditional fourth based on playing time) because they liked that depth and also because they really liked rookie JaCorey Shepherd in the nickel role.

Regardless of whether the trade was made because they also didn't like Boykin's stated unhappiness with that limited role, the move became a much bigger topic when Shepherd tore his ACL Sunday and was lost for the season.

Now, the defensive backfield is one massive tryout. Cornerback Byron Maxwell and safety Malcolm Jenkins are going to be out there, but even they could have multiple roles. Filling the slot corner position is an open competition this week among second-round draft pick Eric Rowe, Jaylen Watkins, and E.J. Biggers, but Kelly indicated that the search could be expanded next week if the results aren't impressive.

"We're going to rotate a lot of guys in there," Kelly said. "Watkins will be in there, Eric Rowe will be in there, Biggers will be in there, and we all know that we have Walter [Thurmond] and Malcolm, but we had already planned for the first two weeks of just using corners in there anyway. We'll make an adjustment if need be after this Colts week."

Count on the adjustment, and if it is the logical one, then Thurmond will become the slot cornerback. It is a position he played in a Super Bowl for the Seattle Seahawks. Until the Eagles switched him to safety, Thurmond was only a cornerback in the NFL.

Kelly's logic might be different, however, and the Eagles don't mind trying to make cats bark and dogs meow. Rowe, put at cornerback by the Eagles, played almost exclusively at safety in college.

"My main focus has been on the safety position because it's a new and different world for me, but I would just have to go and pick up the playbook for the position," Thurmond said about taking reps as the slot corner. "I'm very used to it."

Jenkins, who played the slot when Boykin was unavailable last season, is another possibility, but Kelly would probably prefer to put him at safety and forget about him. Maxwell, according to Jordan Matthews, was the toughest cornerback he faced last season in the slot.

"I wouldn't have a problem with it," Maxwell said. "I don't mind getting in there."

So, they have choices. It just remains to be seen how the dominos fall after the decision is made on the slot cornerback. If it is Rowe, then Nolan Carroll has to come through as the other starting outside cornerback along with Maxwell. If it is Thurmond, then Earl Wolff would have to do the same as the starting safety alongside Jenkins. If it is Watkins or Biggers who wins the job, then the choices get a little easier and the backfield has more room for error.

"We still have yet to play a preseason game, so we've got a long way to go," Kelly said.

True enough, but as one puzzle leads to the next, solving them all gets more difficult. Someone will play the left guard and right guard positions for the Eagles. Someone will get the outside linebacker snaps opposite Connor Barwin. And someone will be the slot cornerback.

"The game is going to let it shake out," Maxwell said. "When the lights come on, it's going to shake out itself."

Fitting the pieces together is the challenge, but even the best coach doesn't know for sure until then whether he has really collected the right ones.

@bobfordsports