"I was cool with it," he said earlier this week.
It was unlikely that Celek would have said otherwise. He did acknowledge the obvious in the Eagles' drafting Ertz.
"They're trying to find somebody to replace me," Celek conceded. But there is reason for the 28-year-old tight end to be optimistic about this season in Kelly's offense.
Kelly answered a question about having three starting-caliber tight ends this way: "We're going to go three tight ends in a game." So Celek, Casey, and Ertz should see plenty of action.
The success the Patriots have had with multiple pass-catching tight ends has many predicting that Kelly will use his tight ends in the same manner and have similar results.
But how realistic is that? Kelly plans to mold his offense to the skills of his players and it will certainly feature less running, but he did not throw to his tight ends very often at Oregon.
In Kelly's four seasons as head coach, Oregon tight ends caught 16.3 percent of completed passes. By comparison, Penn State coach Bill O'Brien, one of the architects of New England's tight end-heavy offense, had his quarterbacks complete 30.1 percent of their passes to tight ends in 2012.
The difference probably had more to do with personnel than anything - Kelly had explosive wide receivers and pass-catching running backs at Oregon - but scheme played a part as well.
For most of his time at Oregon, Kelly's tight ends stayed in to block for his often-used zone-read plays. But the writers at FishDuck.com, a blog devoted to analyzing Oregon football, discovered a new wrinkle in Kelly's use of the tight end.
In the Fiesta Bowl, Kelly's final game at Oregon, he had tight end Colt Lyerla releasing into the secondary on several plays. This gave Kansas State, when it had six defenders in the box, an unblocked defender to stop the zone read, but it also gave the Ducks an open receiver over the middle or a decoy that drew defenders.
Lyerla pulled in a pass for 23 yards on one play and opened up space for tailback Kenjon Barner, who caught and ran for a 24-yard touchdown on another. Kelly may not lean on the zone read in the NFL, but those plays could signal one way in which Kelly plans to utilize the tight end.
Celek said he has spent a lot of time watching film of Oregon's tight ends.
"They're allowed to work the middle of the field," Celek said. "You've got a lot of room there in the middle of the field the way the offense is set up. I like it, not only for the tight ends but for the slot receivers or if there is a second tight end."
Kelly's tight ends may not have caught many passes at Oregon, but they contributed more in passing yards (19.9 percent) and touchdowns (23.1 percent). With the outside receivers pecking away at the edges, often with quick screen passes, the middle of the field opens up.
Kelly likes the mismatches he can get with tight ends, especially with multiple sets. If opposing defenses use two or three linebackers to cover them, Kelly said he'll spread them out and throw. If they use defensive backs, he'll just run the ball."
"So, pick your poison," he said.
Kelly's offense places a premium on skill position blocking, but the tight end will have the most responsibility. Celek has never been a great blocker, but he has gotten better. Casey, a former fullback, isn't afraid to get dirty.
Ertz wasn't asked to block as much in college. His development there could determine his playing time. Ertz will miss the rest of spring workouts because of an NFL rule that prohibits rookies from practicing until after graduation.
A good route runner at Stanford, Ertz could be employed various ways in the passing game. He could just as easily be split wide than in the slot.
The Eagles, of course, have other outside options. They have a stable of receivers and running backs, probably the primary reasons why the tight ends won't be featured as prominently the Patriots' Rob Gronkowski and Aaron Hernandez.
But it remains speculation until Kelly finally unveils his offense.
"I'm excited to get going," Celek said, "and actually see how this works in a game."
Contact Jeff McLane at firstname.lastname@example.org. Follow on Twitter @Jeff_McLane.