The Arkansas defensive coordinator said Manziel was a lot like what the Hogs saw in week two in Louisiana-Monroe quarterback Kolton Browning -- except Manziel is faster.
"They are very similar," Haynes said after practice Wednesday, "in the way they scramble. But they are two different players. This kid is probably a lot faster.
"When I say that, everyone gets nervous. We have to be very disciplined to stay in our running lanes and stay in our coverage."
The Hogs rolled between Walker Pavilion and the new practice fields south of the indoor facility as rains came through Fayetteville during the Wednesday practice.
Haynes was asked about the condition of starting safety Eric Bennett, limited by injury in Tuesday's practice.
"He's day-to-day," said Haynes, who said Alan Turner and Jerry Mitchell are getting practice time ahead of the trip to College Station to play A&M's Aggies.
"We are working those two and also Ross Rasner. Jarrett Lake is getting some work at the star position so Ross can go back there (at safety)."
Haynes said true freshman Nate Holmes is getting work with the second group at cornerback and could help there this week. Holmes moved from running back to the secondary last week.
Asked if Holmes was close to being ready, Haynes said, "I think he is. He's still learning. He's getting mixed in with the twos. We may have to throw him into a game. We probably wouldn't ask him to do a whole lot, but there are some things he can do."
This week's package will be built around battling Manziel, one of the SEC's best dual threat quarterbacks. Browning wrecked the Hogs three weeks ago. He passed for 412 yards and ran for 69.
"He's the heart of the team," Haynes said of Manziel. "As he goes, they go. He gets out in space and breaks ankles. He will challenge our discipline."
Haynes said Manziel isn't always trying to run when he scrambles. He's just "buying time for his receivers to find an open area."
The Hogs have given up big numbers in the passing game. Haynes said that's a coverage issue more than a rush issue.
"Think it is a lot of coverage," he said. "We do a good job of rushing the quarterback, but it's the quick game that gets us. We don't want them to nickel and dime us down the field with the quick game. We have to use our eyes and get better in our drops and challenge the routes.
"We can get some pressure with our front four, but we can't let them have the first read. We have to make the quarterback go to the second read and that means taking away that first one."
Haynes also said the Hogs can't just do one thing on defense.
"We'll have to mix it up," he said. "We can't go crazy with a bunch of man. We've got some young guys. And we can't just sit in zone. We have to challenge them when we are in zone, jam 'em up and not let them in the vertical entry so easy."
Haynes said senior Tenarius Wright, moved from linebacker to end last week, could play both spots based on the packages the Hogs utilize from week to week.
"He's doing a good job," Haynes said of the work Wright is getting at end. "That's his natural position. But we are going to move him around. He'll play some linebacker and some end."
Wright started at middle linebacker the first three games with Alonzo Highsmith moving into that spot last week. Terrell Williams took Highsmith's spot at weakside linebacker.
Haynes mentioned Highsmith as one of the players who has stepped up in a leadership role and the change to "mike" linebacker might have helped in that process.
"I think the move to mike made him feel a whole lot more comfortable," Haynes said. "He was productive there. His confidence is up.
"Ross Rasner has always been a good leader," Haynes said. "He has the ability to communicate. I think Alfred Davis has been a good leader, too."
Wright said there are plenty of leaders. He's been quick to deliver a message, even while transitioning to his old spot.
"I didn't have a problem going back to end," he said. "And I tried to deliver the message that we have to stay together and focus on just getting better. It's about staying together and making a business trip this week."
Wright said film showed his problems at linebacker.
"Where I saw I had breakdowns was out in space," he said. "Myself, I am taking the opportunity back at end to try to get better and help the team. I'm for it. I'm for moving between (linebacker and end) in whatever way I can help. We have others in the front doing the same thing. Chris Smith and Colton Miles-Nash are doing similar things between down at end and up at linebacker."
Williams played both middle and weakside linebacker in August in preparation for just this kind of move. He said either spot is fine.
"I've had it probably even leading up to this and I like them both," he said. "I can handle this just fine. I learned all of the assignments in camp. I like will because it allows you to make a lot of plays."