They fed off the energy and excitement he showed in meetings and on the practice field. They were certain his exotic schemes were exactly what was needed to turn the worst defense in franchise history into one of the NFL's best.
Then Ryan did what members of his family do. He shared some of his confidence with reporters.
Tired of hearing about the juggernaut the Philadelphia Eagles were putting together, Ryan said: "I don't know if we win the all-hype team. I think that might have gone to somebody else, but we're going to beat their (rear) when we play them."
While some of his players may have felt that way, too, they weren't about to say it.
"We were like, 'Rob, what the (heck) are you doing?' We don't know you, man. You can't come in here and do that,'" linebacker Bradie James said.
At the time, it seemed as if Ryan was just keeping up the family tradition of talking big, like his twin brother Rex and his dad, Buddy.
Now, with the teams preparing to meet Sunday night, that bulletin-board material looks awfully clever.
Ryan's play-calling and personality has transformed Dallas into the top-ranked defense in the NFC. The Eagles, meanwhile, are 2-4 and looking up at the Cowboys (3-3) and everyone else in the NFC East.
Ryan's early August braggadocio hasn't been forgotten by either team, and is certain to be played up during the national, prime-time broadcast. It adds another layer to a rivalry once fueled by Rob's dad, and to a matchup filled with ramifications for both teams.
"Shoot yeah! You know I'm up! I'm drinking Red Bulls all night!" James said in a Ryan-esque voice.
Through six games, the Cowboys have adopted the personality of their sideline leader, save for the long, stringy hair and oversized belly.
Using exotic formations and an aggressive mindset, Dallas is allowing the fewest yards rushing in the NFL.
Only five teams allow fewer yards per play. Nobody has scored a touchdown in the first quarter against the Cowboys; they've given up just nine points in the opening period. They also recently held New England to 17 points, shattering the Patriots' streak of 13 straight games with at least 30 points.
And, to think, they're doing this with virtually the same group of guys who last season allowed more points and yards than any of the 50 previous Dallas defenses.
"I give him 100 percent credit," star linebacker DeMarcus Ware said. "He always talks about the players go out there and make the plays, but he gets out there and gives us the opportunity to do that."
The Eagles present a fascinating challenge.
Because of McCoy and Vick, Philadelphia has the top rushing attack in the NFL. The Eagles are also coming off a bye, and coach Andy Reid is 12-0 when given an extra week to prepare for a foe.
Then again, Philadelphia is 0-2 at home and has lost five straight there, counting the playoffs. The Cowboys also have beaten the Eagles in four of the past five meetings, counting the playoffs.
Philadelphia's lone recent win over Dallas included Jackson catching four passes for 210 yards, including a 91-yard touchdown that he punctuated by stopping just shy of the end zone and tipping over the goal line.
That was among many big plays the Cowboys' secondary gave up last season, which is partly why team owner Jerry Jones tried to sign the top free agent cornerback on the market, Nnamdi Asomugha; he went to the Eagles instead, part of the supposed "Dream Team" they were putting together over the summer.
Ryan and Jones were seen on cell phones on the playing field during the negotiations for Asomugha. Everyone saw it, including Terence Newman, the starter who was most likely to have been dumped had a deal been struck.
It's a safe bet that Ryan will have him motivated Sunday.
"If you don't get up playing for Rob, then you just don't have a passion for football," said Mike Jenkins, the other starting cornerback. "He has a lot of confidence on what he has, and that's what builds confidence on the team."
James said the Cowboys have seen — and heard — all sorts of things from Ryan this season. They can't help but laugh and keep listening because he's gotten so much out of them.
Even back in early August, James had been around Ryan enough to not be too surprised about what Ryan said about the Eagles. That doesn't mean he liked it.
"I'm like, 'Rob? You picked the Eagles?! C'mon, man, pick St. Louis!'" James said, laughing. "But, here we are. It's time to play ball."