CARY, N.C. -- Dave Sarachan has seen a few defenders develop during his coaching career. He was witness to Carlos Bocanegra's final season with the Chicago Fire before the United States stalwart departed for Europe. He also was present for some of Eddie Pope's best years in a U.S. national team jersey.

Now as Sarachan's time as caretaker for the U.S. enters its final few months, part of his remit is to help move along the international careers of the next generation of center-backs. Ahead of Tuesday's friendly against Paraguay, he's seeing some intriguing prospects up close in Matt Miazga, Cameron Carter-Vickers and Erik Palmer-Brown. All have excelled for the U.S. Under-20 national team in the past, and all are currently on loan to European clubs from Premier League sides.

"I think we have a good generation of center-backs developing," Sarachan said on Sunday at the team's hotel.

Good thing, because the window of opportunity at the position has been thrown wide open. Most of the defenders used during the failed attempt to qualify for the 2018 World Cup will be well into their 30s when qualifying for 2022 begins. A notable exception is Wolfsburg's John Brooks, who is just 25, but he has proven to be injury-prone for much of his career.

So with that in mind, Sarachan is keeping an eye -- both when he can -- on the trio of center-backs in camp. And while playing the ball out of the back is a must for a central defender, Sarachan's focus is on the defending side of the ball.

"It's defending in all sorts of moments that appear in a game, in transition moments, counters, whether it's isolated in 1-v-1, keeping-your-feet-moving defending," he said.

"Or if it's off the ball defending, not being a ball-watcher but understanding that when the ball goes wide, as a center back, you've got to take care of a lot of different things -- the ball, your opponent, the second runner, your partner.

"So it's multitasking which is the developmental part of experience. It's not just about one thing, it's about two or three or four things."

Palmer-Brown, who recently was signed by Manchester City, is currently on loan to Belgian side Kortrijk. Having joined in midseason, he has made just one league appearance, and he admits he's playing a bit of catch-up with his new club.

Matt Miazga and Cameron Carter-Vickers, along with Erik Palmer-Brown, continue to make progress, with Tuesday's friendly with Paraguay their next test. Photo credit should read Michael B. Thomas/AFP/Getty Images

"I think it's going good," the 20-year-old told ESPN FC prior to Sunday's training session. "The lifestyle, everyone speaks English there, so it's been an easy transition in that aspect.

"But it's really demanding physically. For like two weeks, I was running after training for an hour. For me, it's kind of old-fashioned in that sense. That was what was difficult for me."

That said, Sarachan says he hasn't detected much rust in Palmer-Brown's game.

"His feet are good, his distribution has been good," Sarachan said. "The little bit of defending we've seen -- because we haven't had that many full scrimmages -- seems like he's comfortable."

Carter-Vickers is undergoing his first full season of first-team action, having made a combined 29 appearances for Ipswich Town and Sheffield United while on loan from Tottenham Hotspur. Carter-Vickers is a defender who seems as wide as he is tall, but also has some skill to go along with his physicality.

"This guy is steady, man, steady as a rock," Sarachan said of Carter-Vickers. "He's hard, he's alert, he's better than you think with the ball.

"He looks like a running back, but as you can imagine, when the moments come that he's got to get in on a play, or not allow a guy to get behind him, he knows how to use that body. There's a lot of big guys that don't, and there's a lot of little guys that do, but he's a big guy that knows how to use his body and moves better than you think. He's just been very consistent all week long."

Of the three, Miazga seems the furthest along, which isn't a surprise given that at 22, he's two years older than both Palmer-Brown and Carter-Vickers. He's made considerable use of nearly two seasons on loan at Vitesse from Chelsea. Last season he helped lead Vitesse to the KNVB Cup, the first major trophy in the club's 125-year history.

With two months to go in the season, he's played more than 30 matches, including some in the Europa League, and the challenge of playing twice a week is one he welcomes.

"There's not time for excuses, you've got to perform at a high level," he said. "There's competition, with grown men trying to take your spot. You're the same.

"Obviously it's good competition, but that's just the reality of it. You have to be fully ready, consistently focused on performing at a high level, no slip-ups, and just continue playing, and I've been able to do that playing a lot of minutes this year."

The right-footed Miazga has become more versatile by playing nearly two seasons as a left-sided center-back. He's also taken on more of a leadership role within the team.

"I've been slowly embracing that [role] and taking that to my game, and I've seen it paying dividends a lot in terms of communication, awareness and helping my teammates by organizing," he said. "I think that's what I've improved the most, my communication, my awareness and my organization."

His progress has been noted by Chelsea, who Miazga says pay him a visit every five to six weeks to gauge his progress, and give him feedback on his performances.

"They're very engaged," he said.

His focus remains on the end of the season with Vitesse, and then he'll speak to the Chelsea brass about what's next, though it remains to be seen if manager Antonio Conte will even be in charge after the current campaign.

"There's a lot of what-ifs. That's how football works," Miazga said with a shrug and a smile.

Sarachan has spent much of the week trying to establish chemistry between players, but Miazga, Carter-Vickers and Palmer-Brown have a built-in advantage. All three played for the U.S. at the 2015 FIFA U20 World Cup. Carter-Vickers and Palmer-Brown played in the tournament again two years later.

"We're just pushing ourselves along in this journey," Miazga said. "We have a good connection. We've been playing in these national team programs for a while and hopefully we can continue working hard and establishing ourselves in the senior team."

Tuesday marks the next step.