Where do NFL teams go to find the most pro-ready players? NFL.com's Pipelines to the Pros series explores which schools, at each of eight positions over the last 20 years, have been providing NFL clubs with not only the most draft choices but also the most impactful pro players early in their careers. And beyond that, an examination of why those schools are so successful and the factors that contribute to a college program's ability to maintain pipeline-like development at a particular spot on the field.

Today, in the fifth of eight installments, we examine the schools vying for the title of Tight End U.

Dallas Clark's football resume includes being a first-round draft selection, a Pro Bowl and All-Pro player, and Super Bowl champion, all of which was made possible largely because he was a dynamic receiving threat in eight of Peyton Manning's 13 seasons with the Indianapolis Colts. But coming from the University of Iowa, where tight ends block first and foremost, he always felt like he was more than just a pass catcher.

"When the Colts exploded and we all went our separate ways, and I went to Tampa, maybe I wasn't good enough anymore, but I was turned into a third-down tight end, and it just crushed me," Clark said. "Because I didn't feel like it was football. I wanted the coaches to feel good about running the football right behind me. It was a walk-on mentality from Iowa that I never let go of."

Eighteen years after Clark left Iowa for the NFL, Hawkeyes tight ends rank third in NFL.com's Pipeline to the Pros series, which identifies schools that develop the most NFL-ready players at specific positions. And the emphasis longtime coach Kirk Ferentz's staff places on blocking at the position remains a big reason for it.

Two years ago, for the first time in NFL draft history, two tight ends from the same school where selected in the first round in Iowa duo T.J. Hockenson and Noah Fant. A few months earlier, former Hawkeye George Kittle established himself as the NFL's best tight end with a record 1,377 receiving yards, although Kittle's blocking is, of course, stellar as well.

Credit the Hawkeyes' more traditional offensive style as at least one factor.

To help fuel a committed running attack, Iowa still requires a quality in-line "Y" blocker at tight end, something still in demand at the pro level. The way college football is trending, the Y might as well stand for "Y have one?"

Long gone are the days of college tight ends being blockers first; in the modern game, far more can stretch the field as a receiver than can drive a defensive end or linebacker off the line of scrimmage on a power run. The NFL, to be sure, has spread tight ends into the slot for years and made stars of athletic mismatches like Kansas City's Travis Kelce, Philadelphia's Zach Ertz, and many others. But at the pro level, there remains a baseline appreciation for in-line blocking at the position that college spread offenses don't as often call for.

Meanwhile at Iowa, Ferentz maintains the emphasis. Indeed, his tight ends coach, son Brian Ferentz, was an offensive lineman as a player and coached Iowa's offensive line before taking on his current role. He has Clark – who maintains a home in Livermore, Iowa – return to give a speech to the team in training camp on an annual basis.

"I think in general terms, it is (disappearing)," Ferentz said of the Y-position in college football. "A lot of people are now playing that guy off the ball. That's a more customary alignment. Several teams we play, their standard formation is three wides and a tight end who lines up off the ball so he can block back across the formation, release easier, all that. It gives you more flexibility. We would be near the top, in our conference and nationally, as for as using a guy up on the ball, on the line of scrimmage. It's part of our DNA."

That's not to say Iowa doesn't spread tight ends out at times; in two-tight end sets featuring both Hockenson and Fant, for instance, Fant would commonly split out as a receiver. But after Fant set Denver Broncos records for catches (40) and yardage (562) by a rookie tight end last year, new offensive coordinator Pat Shurmur described him as "frankly … pretty gritty" as a first-year blocker.

Kittle played a more traditional Y role at Iowa and, according to Ferentz, could have been more productive as a receiver had he not endured foot and ankle injuries.

Clark believes Ferentz's background in the NFL – he was an assistant coach with the Browns and Ravens for six years – is part of why he maintains a stronger belief in the importance of blocking at the position. The coach has found recruiting tight ends to be more of a projection than it once was, because high schools have gone the way of the spread offense as well. So Ferentz and his staff look for a certain body type – long and strong, but not necessarily big – and builds them into more traditional tight ends upon arrival.

"Hockenson didn't play in high school the way we would use a tight end. Same with (former Houston Texans TE) C.J. Fiedorowicz. He was a big guy in high school but was still flexed 7 yards from the tackle," Ferentz said. "But learning to block isn't the hardest thing in the world."

NFL coaching staffs are facing the very same projection, faced with evaluating college tight ends whose game tapes show plenty of speed and skill for route-running and pass catching, but not as much in the area of blocking, particularly on the line of scrimmage. When the modern rookie tight end arrives at training camp, pro coaches know more of what to expect from them as receivers, while blocking is more of an unknown.

"On Sundays, guys are still putting their hand on the ground and they still have to knock back the guy across from them. There is always going to be a need for that guy," Clark said. "If (an NFL team) needs a Y, where are they going to go to find a guy who already has the footwork and technique to block on the line of scrimmage? Not many places, but Iowa is one of them. At Iowa, the blocking drills for tight ends don't get cut down to five minutes so they can get more time for 7-on-7 or routes versus air. It's still at the core of the practice."

The University of Miami topped the tight end rankings in this series by a relatively wide margin, but did so based largely on a reputation buried in yesteryear. The Hurricanes' top-rated tight ends were Jeremy Shockey, Bubba Franks, Jimmy Graham, Greg Olsen and Kellen Winslow Jr., none of whom have played a down for UM in 10 years or more.

But 17 years after the Colts drafted Clark No. 24 overall, NFL general managers needing immediate returns from a young tight end are still finding them in Iowa City.