Ryan Walters is a secondary guru. It's clear Purdue defenders have a lot to learn.

First-year Purdue coach Ryan Walters came to West Lafayette with the reputation as a defensive guru.

His time as defensive coordinator at Illinois produced a swarming secondary, placing multiple defensive backs in the NFL with a scheme lauded by his contemporaries for its creativity and ability to confuse opposing offenses.

Coaches can dial up the perfect play, but they need execution to make stops. Against Fresno State, the Bulldogs offense consistently beat Purdue's secondary, allowing receivers to break free and generate big play after big play.

A guru of his own, Jeff Tedford's offense racked up 371 yards passing and four touchdowns, leading the visitors to a 39-35 win over Purdue in Walters' debut.

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"Just sitting from the side and knowing what's called and within the framework of the scheme, there was the one touchdown we just had a coverage bust," Walters said. "... Obviously, that leads to bad plays.

"I thought we just played on our heels too much and didn't play with aggressive technique in our man coverage, especially in the slot. So again, those are all things that we need to work on and will watch film from and get better. We'll improve from Week 1 to Week 2."

The eye in the sky doesn't lie, and film study after Saturday's performance won't be kind to the Purdue secondary. Purdue started true freshman Dillon Thieneman at safety, but the Boilermakers have experienced returners in Cam Allen and Sanoussi Kane who should be able to erase mistakes on the back end.

Purdue was in position to get off the field on Fresno State's first scoring drive, but poor execution gave the Bulldogs new life. Allen shadowed tight end Jake Boust on a third-down crossing route. Allen wrapped up Boust short of the marker, but Boust broke free for a 12-yard gain and a first down. One play later, transfer safety Botros Alisandro jumped a crosser, allowing receiver Erik Brooks to come wide open in the end zone for a 29-yard touchdown.

Tedford's offense dialed up another great call for its second touchdown. On 1st-and-goal from the 8-yard line, Fresno State quarterback Mikey Keene faked a read-option play to running back Elijah Gilliam, pulling the ball and turning up field. Keene's move forced Thieneman to abandon his coverage and charge toward the quarterback. Once Thieneman committed, Keene pulled up and passed to a wide-open Jalen Moss for the score.

"I felt like when we weren't aggressive, and we weren't really dialed in to doing our jobs. We gave up unneeded yardage," Walters said. "We'll go back and look at the tape and see where some of the breakdowns were, but just from my vantage point... A guy was misaligned here or didn't make the right read there, or not just being confident in technique. So, we'll go back to the drawing board if you will and find ways to continue to improve."

For all the miscues and breakdowns, Purdue's defense did put it in position to pull out the win. Thieneman — the Purdue legacy who struggled at times — made the play of his young career late. On the 3rd-and-8 with 5:25 left in the game, Thieneman drove from his deep safety position toward a pass lofted up the sideline. The Westfield grad showed his impressive closing speed, meeting Mac Dalena at the ball, leaping through the receiver, securing the catch and getting a foot inbounds before falling out of bounds.

A Hudson Card 44-yard completion to Deion Burks setup Devin Mockobee's 11-yard touchdown run one play later, putting the Boilermakers ahead 35-32 with 4:36 left.

"It gave us an opportunity to go ahead right there," Walters said of Thieneman's pick. "He played how we see him in practice, so it wasn't surprising. There's a reason why he's a starter. There's a reason why he's making the plays that he's making. It's because he's not only talented and capable enough to do it, but he puts in the work, and he practices the way he plays."

The Purdue defense made one key stop, but Fresno State had more than enough time to respond. The Bulldogs marched 79 yards in nine plays with 76 yards coming through the air, capping the drive with a 22-yard pass from Keene to Brooks. Brooks finished with a game-high nine catches for 170 yards and two touchdowns.

Saturday's season opener was a learning experience for the Boilermakers, or at least it better be. Their mistakes appear to be correctable. One or two fewer mistakes and maybe Walters' debut ends with a win. Now, it's back to the drawing board, and Walters and his staff have to continue coaching up their players.

"Obviously this is disappointing," Walters said. "Nobody wants to start off with a loss. But we've also talked about how adversity is guaranteed and it's about how we react. ... We will get better."

This article originally appeared on Indianapolis Star: Purdue football secondary a key weakness in loss to Fresno State