The NFL Hall of Famer made it chic for the big guys to catch passes and run downfield when it was more popular for them to be blockers or outlet receivers.

Now, four decades later, Clark is carving out his own niche in a very different NFL.

Tight ends are expected to catch more passes than throw blocks, and like Mackey, Kellen Winslow, Shannon Sharpe and Tony Gonzalez before him, Clark has learned how to use his unique skills to create defensive mismatches.

"I think Gonzalez, and Mackey back in his heyday, really changed the position," Clark said. "I think they really gave guys like (Antonio) Gates and others a chance to excel."

Clark certainly fits in, too.

At 6-foot-3, 252 pounds (1.92 meters, 114 kilograms), he's better known for his speed, his ability to run after the catch and his aptitude to stretch the field.

Since the start of 2008, no NFL tight end has been more productive than Clark. His 141 catches and 1,616 yards over the last 25 games rank No. 1 among all tight ends even though he has not yet gone to a Pro Bowl.

That could change this year. With Gonzalez out of the AFC, and Clark tied for second in the NFL with Wes Welker with 64 receptions, Clark seems like a certain pick.

In addition to the sterling numbers, records are falling at a breakneck pace, too.

In 2007, Clark broke Mackey's four-decade-old team records for receptions and touchdowns by a tight end in one season. Last year, Clark smashed his own record for receptions in a season (77) and broke Mackey's 42-year-old mark for yards in a season (848). This year, he's on pace to shatter those numbers again.

But Sunday may be the most awkward record-setting moment yet.

Clark needs one catch to break Mackey's Colts' record for career receptions by a tight end (320), and it's likely to happen in Mackey's old stomping grounds in Baltimore _ the city that hasn't forgotten the team's midnight move to Indianapolis.

So Clark's friend, three-time MVP Peyton Manning, has added the title of diplomat this week.

"(Clark) had a great appreciation for who John Mackey was before he got drafted by the Colts. I know he has more now," Manning said. "Whether they played in Baltimore or we play in Indianapolis, you still have a great appreciation for great football players. That would be a tremendous accomplishment and a great credit to Dallas. I think it would be special for him because he knows what a great player Mackey was."

Perhaps nobody understands the situation better than Manning.

In college, Manning won the Unitas Award, then was taken No. 1 overall in the 1998 NFL draft with the clear objective of breaking Colts great Johnny Unitas' records.

Clark won the Mackey Award in college, then was taken by the Colts in the first round of the 2003 draft. The goal, of course, was to become the best tight end in Colts history, which meant supplanting Mackey, a star of the 1971 Super Bowl who caught a tipped 75-yard touchdown pass in the Baltimore Colts' 13-10 win over Dallas. Now in his late 60s, he suffers from dementia.

While the Colts have used Clark in the slot, as a deep threat over the middle and on reverses, Clark has made his greatest strides along the offensive line. When Clark arrived in Indy, he came with the tag that he could catch passes, not block.

Over the past two years, though, Clark is showing he can do both jobs effectively.

The Colts have increasingly run to Clark's side this season, and in last weekend's comeback against New England, his block helped spring Joseph Addai for the 4-yard touchdown run that got Indy within 34-28.

It's something Clark takes pride in.

"Blocking was always a concern whether I could do it or not," he said. "But I've always been a proponent of proving people wrong. I want to be a complete tight end, not just a receiving tight end. That's what differentiates our position, being able to do both."

Mackey couldn't have said it better himself.

"I would tell the people of Baltimore that Dallas respects the right guys," Manning said. "He has an appreciation for what John Mackey accomplished."