Since the new league year started on March 9, the Colts have lost three starters and added one backup. Though their moves (or lack thereof) are not unexpected, they do open up holes and question marks on the roster: namely in the role of three "starting" spots that have now opened up. What will the Colts do to fill them?
The Indianapolis Colts lost tight end Coby Fleener in free agency to the New Orleans Saints, meaning that they lose a guy who has played in 60 games and started 48 for them over the past four seasons. He was the Colts' receiving tight end and was consistently one of the team's top three receiving targets. The Colts opted to let him walk in favor of Dwayne Allen, however, and that's where any look at how the team will replace Fleener must begin.
The Colts choose to re-sign Allen instead of Fleener, and based on Fleener's comments about the Colts not showing much interest, it seems that Allen was the Colts' choice all along. Allen is the better overall tight end and was the right choice for the Colts. At the same time, however, two other aspects come into play when talking about the Colts replacing Fleener: firstly, the receiving threat; and secondly, the number two tight end.
While Allen is a good and capable receiver, he's not quite at the level of Coby Fleener in that area. It is likely, however, that he will be the one counted on to step up and produce in the passing game, and he can do that as long as the Colts give him the opportunities to do so. Probably the biggest component in replacing Fleener will be the coaching staff, as they need to utilize Allen properly and let him make some plays as a receiver too. Last year, the Colts kept him in mainly as an extra offensive lineman, and while he should have still been used more in the passing game regardless, it was allowed by the fact that the team had another tight end who could pick up the slack in the receiving game. The team doesn't have that anymore, and it means that the coaching staff will need to give Allen the chance to produce if they want receiving production from the tight end position. At the same time, the wide receiving corps of T.Y. Hilton, Donte Moncrief, and Phillip Dorsett will likely see the bulk of the targets, so they too could help make up for the loss of Fleener, but that still doesn't make up for the tight end position and Allen will need to step up there - which he can do, as long as the Colts let him.
For the second question, the Colts need a number two tight end. Allen has been the Colts' unofficial number one tight end when healthy, but Coby Fleener has been there every week to start a number of games (47 of them) and be essentially tight end number 1b. Last year, the Colts used multiple tight end formations on 388 snaps, so they'll clearly need someone else to step up. They may choose to use less two tight end formations, but they still need a backup. That's where Jack Doyle comes in. Though he's still technically not signed, the Colts tendered him and it's very likely that he will be back, giving the Colts a good number two tight end option. Doyle can block and catch, and he has shown the ability to be an underrated contributor to the offense.
So while the Colts did let Coby Fleener walk in free agency and will need to replace him, they have good players to do so in bringing back Dwayne Allen and Jack Doyle. If the coaching staff uses their tight ends properly, it's unlikely that we'll see the Colts offense experience a big dropoff after losing Fleener despite his production over the past few years.