Mike Pettine is up front about it when asked how rookie safeties Duke Williams and Jonathan Meeks are progressing in his defense.

“Both those guys, I just think they’re a little overwhelmed right now with the scheme,” the Buffalo Bills’ defensive coordinator said recently after a spring practice. “We had a very simple camp for them, the rookie camp, then came in the very next day and threw a whole bunch at them. So I think both those guys are going through that rookie learning curve.”

That’s not to say Pettine is disappointed – or surprised – by where Williams and Meeks are in their extremely green professional careers.

“Those two have flashed what we saw as we were evaluating them from a draft standpoint. I think both of them have solid futures in this league, but it’s just so early for them,” he said. “Sometimes it’s hard to evaluate them because you can just see the gears grinding. I’ve seen it with so many young safeties. To me, that’s probably the hardest position defensively to learn.”

Exhibit A: The coverage assignments.

At Nevada, Williams played a Cover 4 scheme – four deep defenders guarding one-fourth of the field – on 95 percent of plays, by his estimation.

At Clemson, Meeks said the Tigers had five basic coverage schemes they would run.

With the Bills, Pettine says: “here we’re working with 16, 17, 18 different coverages.”

“That was really the only thing I’ve known,” Williams said of playing Cover 4. “Here, it’s different sub packages, different schemes … it’s really complex.

“We’re installing a lot of defenses and different schemes every single day. As we get repetition, we’re getting better and better each day, so that’s what it’s about: just fixing your mistakes you made the day before and getting it right the next day.”

That leads to Exhibit B: The communication.

“There’s so many moving parts and there’s so many calls to make,” Pettine said. “They’ve got to communicate with the linebacker, they’ve got to communicate with the corner and they’ve got to communicate with the other safety. It can change in a heartbeat based on pre-snap alignment and that’s a lot for a young guy to process.”

Think of the safeties as the quarterbacks of the defense. It’s their job to make sure each player is in line.

“You’ve got to make sure everyone’s doing their job,” Williams said. “It’s tough when you’re new to it, and you’ve got veterans and you’re trying to get them aligned.”

It’s added up to some long hours for Meeks and Williams.

“You have to study a lot. You have to be a student of the game outside of the facilities,” Meeks said. “It’s a long day here. We work out hard, we practice hard. When we go home, rest up, look over what you’re going to put in for the next day. It’s constantly adding things and adjustments you’ve got to keep up with from Day One. It requires a lot of time.”

Let’s call that Exhibit C: Time.

“Once we left rookie camp, their repetitions go down just because we have basically the varsity guys here, so it’s hard for them to get as many reps as they did in that first camp,” Pettine said.

Meeks and Williams have gone through 11 practices since being drafted, three at rookie camp and eight organized team activities. That still puts them behind veterans at the position like Da’Norris Searcy, Mana Silva and Aaron Williams, who had the benefit of taking part in the team’s voluntary minicamp and offseason conditioning program.

“A lot of the concepts we’re playing here were played here last year,” Pettine said. “I mean, a lot of stuff is pretty standard NFL stuff.”

That means that even though Aaron Williams switched positions from cornerback, he’s not necessarily behind.

“I think because we made the switch before we started anything, so he was really learning the defense as everybody else was, so it’s not like he played corner for two weeks with us here and all of a sudden we said, ‘Oh by the way, we’re going to make you a safety,’ ” Pettine said. “We had informed him basically from Day One in April. He was a safety right from then. We evaluated the roster and when we looked at it overall, I was kind of already swayed that way a little bit. We saw him in New York, he was on our draft board as a safety.”

The Bills were comfortable in switching the 6-0, 199-pound Williams because of his versatility.

“Any time you have a safety with corner skills, that’s a big plus,” Pettine said. “He’s covered slot receivers. He’s covered wide receivers, whereas your true, prototypical safety, or your low safety, is more of a guy that might be better than tight ends on wideouts.

“I think that’s the way the league’s trending. You’ve got to match speed with speed. Some of these tight ends now,” he said, mentioning New England’s Aaron Hernandez as an example, “safeties are hard matchups. Now with a safety that has corner-type ability, you feel more comfortable.”

Duke Williams and Meeks have both worked at both safety positions during spring practices.

“It’s all about versatility. Different schemes, we might have seven defensive backs on the field,” said Duke Williams, a 6-0, 190-pounder. “It’s just a wide variety of things I can do on the field. It’s a great fit for me.”

Bills scouts said after Meeks was drafted that he was a difficult player to evaluate because the scheme he played at Clemson didn’t give him many chances to be around the ball.

“That was true. I have a lot of abilities I didn’t get to showcase in college like some other guys and I feel like if I would have had the opportunity or been in the system that allowed me to do that, then I would have went higher,” he said. “Fortunately enough, the Bills did see that.”

The selection of Meeks in the fifth round was considered a surprise, as most national draft publications considered him more of a seventh-round er or undrafted free agent prospect.

“Everybody’s not going to like you in this game. You’ve just got to fight through it,” he said. “I was thankful for them to believe in me. I thought I was a fifth-round player, maybe even higher than that. You’ve got to prove everybody wrong. I’m going to prove the Bills right – that they made a great decision.”

Similarly, Duke Williams has to prove that his off-the-field issues are behind him. He was suspended multiple times as a freshman because of incidents involving alcohol and a fight with a teammate, but he said the experiences made him a more mature person.

“You just learn from those things. You change from when you’re 18 to when you’re 22 years old,” he said. “It was just a growing up thing. Luckily, I was able to learn from those situations and better myself.”

With Pro Bowl safety Jairus Byrd sitting out voluntary workouts – and possibly training camp as he negotiates a contract under the franchise tag – the development of Williams and Meeks will be a story line to watch through the summer.

“It’s a pretty tough position. It’s a great position, though,” Meeks said. “It requires a lot of communication, a lot of leadership back there. Having a good eye for the field. You have to be able to see things before they happen. If you get a good safety who can do that, he’s a special player.”

In Meeks and Williams, the Bills hope they’ve found two.