When Iowa wrapped up preseason camp, coach Kirk Ferentz left the field despondent about a particular position group.

A defensive line replacing three multiyear starters selected in the NFL draft? Nope.

A secondary that lost two multiyear starters at safety? Guess again.

What about the quarterback spot? Ricky Stanzi, after all, had taken his bionic arm and infectious patriotism to Kansas City.

But Ferentz wasn't fretting about the men throwing passes. He had little faith, however, in the men charged with catching them.

Other than senior Marvin McNutt, an All-Big Ten candidate and a bona fide NFL prospect, Iowa's wide receiving corps left Ferentz feeling empty.

"I was really in the tank about that position," he said. "We really weren't doing very well."

McNutt, who racked up 87 catches for 1,535 receiving yards and 16 touchdowns in the past two seasons, shared his coach's concern.

"We thought things were moving a little slow," McNutt told ESPN.com. "And you could see in the first couple games, we didn't click the way we wanted to. I knew we had the talent. Things just needed to happen. When people get a little more game experience, they start playing a little bit better."

Or a lot better.

Kevonte Martin-Manley (11) snagged the game-winning touchdown to bring the Hawkeyes all the way back against Pitt. Reese Strickland/US Presswire

What looked like a weakness for Iowa has become potentially a major strength as the team opens Big Ten play this week at Penn State. The emergence of junior Keenan Davis and redshirt freshman Kevonte Martin-Manley alongside McNutt, who continues to roll, gives Iowa a formidable receiving corps.

Iowa's big three has combined for 58 catches, 880 receiving yards and 10 receiving touchdowns through the first four games. After McNutt carried the corps in the season opener (140 receiving yards, 2 TDs), both Davis and Martin-Manley have come on strong, particularly during a historic second-half rally against Pitt, when Iowa went to an effective no-huddle pass attack that left its fans drunk with the possibilities for the rest of the season.

The Hawkeyes aren't going to "go 100 percent no-huddle," as Ferentz joked last week, but the receiving corps, along with blossoming junior quarterback James Vandenberg, gives coordinator Ken O'Keefe new ways to stretch the field.

"These guys, if you give them a chance, they need to be making plays," O'Keefe told ESPN.com. "The most fun in football is that receiver position."

Iowa's receivers are having plenty of fun these days.

Davis' emergence is more of a relief than a surprise for the Hawkeyes. The departure of record-setting wideout Derrell Johnson-Koulianos left a void, and most expected Davis to fill it, especially after he made strides this spring and turned heads at the spring scrimmage.

But Davis' progress slowed in August, and he recorded only two catches in the opener. The 6-foot-3, 215-pound Davis had a key drop in overtime the next week in Iowa's loss to Iowa State but still finished with five receptions for 95 yards and a touchdowns. He followed it up with a career-best performance in the Pitt comeback (10 catches, 129 yards, TD).

"Keenan Davis is finally realizing his potential a little bit," Ferentz said. "I wouldn't have objected if it happened last year with him. We certainly had plenty of need. ... That's the neat thing about football, especially college and high school football. All players progress at different times. The key thing is that they do progress, and we're starting to see that."

Martin-Manley, a smaller receiver at 6-feet and 205 pounds, plays more in the slot and has benefited from some mismatches in coverage.

"The biggest thing for him was learning where he's going to line up," O'Keefe said. "The second thing is get off the line of scrimmage and run your route, get yourself open. And then once you get all that down, you've got to be able to do it full speed. That's what's happened. He's starting to do some things full speed."

The turning point for the receivers, not surprisingly, came in the Pitt game as Iowa fell behind 24-3 late in the third quarter.

"We all looked at each other and said, 'It's time to make plays, men. We know the ball is going to start flying to us,'" McNutt recalled.

Two passes to Davis and one to Martin-Manley put Iowa at the Pitt 5-yard line, where Vandenberg scored two plays later. Iowa's fourth quarter began with a 14-yard touchdown pass to Davis. Martin-Manley then hauled in touchdowns on consecutive possessions, including the game-winner, a 22-yarder with 2:51 left.

"When that happens," McNutt explained, "it builds a lot of confidence for each other as well as us as a receiving corps."

Iowa will need its receivers to be confident and effective as they face by far their toughest defensive test in Penn State.

"We've been making great strides," McNutt said, "but I wouldn't say we think we’re accomplished yet."