Now, Graham is no longer a secret heading into Thursday night's rematch between the Ravens and Broncos to begin the NFL regular season.
"If you go out there and make a few plays and help your team win the game, it means a lot," Graham said. "That's what I wanted when I came here ... to get an opportunity on defense. To go out there and have a big game, especially against an opponent like that, and help your team win is big.
"I don't know exactly what other teams think. If they're throwing the ball at me every play, then obviously nothing has changed. If they're going to keep testing you, eventually you're going to make the play and it should hurt them in the end."
One year after general manager Ozzie Newsome signed Graham to a two-year, $4.209 million contract, the Ravens have assigned him a pivotal role as a starter instead of Jimmy Smith.
"If y'all try [Graham], he's bound to get his hands on the ball," cornerback Lardarius Webb said. "It's just how hard he works, how hard he studies. Ever since he came in from Chicago, we were all thinking, 'Hey, we've got a special teams corner.' That's what we got him for.
"Once he got here, he started picking balls off and making plays. I don't know where Ozzie found this guy, but he found himself a great corner."
During the regular season last year, Graham recorded 54 tackles, two interceptions and eight pass deflections. By the end of the season, his defensive role had expanded to the point where he started a career-high eight games and all four postseason games. In the playoffs alone, Graham had 32 tackles and seven pass deflections.
Although the former New Hampshire standout has good size at 6 feet, 196 pounds and runs well, Graham's intelligence is what makes him stand out to defensive coordinator Dean Pees.
"I think the biggest thing any corner needs is to be smart," Pees said. "There are a lot of talented defensive backs out there that can run like the wind, and they might even be big, but can't play very well. Guys who can really take that athletic ability and put it to use in the right way, that's what I like about Corey. Corey is a smart, smart football player."
Graham will need all of his acumen and skills Thursday night.
The sure-handed Welker -runs exceptionally well after the catch. He caught 118 passes for 1,354 yards and six touchdowns last season for New England.
In the Patriots' two losses to the Ravens last season, Welker combined for 18 receptions for 259 yards. In the AFC championship game, he caught eight passes for 117 yards and one touchdown with Graham primarily assigned to cover him.
Welker's challenge is what's occupying Graham's attention these days, as he spends long hours studying game tape.
"That's a different animal," Graham said of Welker. "Obviously, when you're playing against a guy like Peyton Manning, that's tough by itself. To bring a Wes Welker out there is a big plus for those guys. He can pretty much do it all in the slot.
"We know what type of caliber player he is. So it's a challenge. We got to go out there and make sure we're ready to play. I'm pretty sure Peyton is going to get his guys the ball. We've got to do what we do out there."
Beyond Welker in the middle, the Broncos' offense is headlined by a tandem of imposing, fast wide receivers in Demaryius Thomas (6-3, 229) and Eric Decker (6-3, 214). Thomas caught 94 passes for 1,434 yards and 10 touchdowns last season, while Decker had 85 catches for 1,064 yards and 13 touchdowns.
"Three 1,000-yard receivers, you rarely see something like that," Graham said. "Golly, they got the deep-ball guy, they got the possession receiver guy. That's typically what you want on a team. You want different guys that can do everything. Yeah, they've pretty much got it all, so we've just got to go out there and play."
The Ravens are counting on Graham to do a strong job against Welker and the Broncos' other wide receivers.
"They said, 'What about the matchup with Welker?' Well, he matched up with Welker last year," Pees said. "It's not like this is his first parade. He's matched up against him before, and we'll try to do the best job we can and help guys when we can help them."
Graham loves challenges. He overcame a tough background growing up in Buffalo, N.Y., went to a football program that wasn't a big-college powerhouse and was drafted in the fifth round by Chicago in 2007 before being relegated to kick coverage.
"Everybody has been talking about Denver, it is what it is, but we're going to go out there and play ball and do what we do," Graham said. "We're confident in what we can do and we're ready to show everybody else what we can do."
A 12-page Ravens/NFL special section having everything you'll need to get ready for the 2013 season.