BUFFALO — After the Buffalo Bills took a chance on Stevie Johnson, the flamboyant receiver decided to return the favor.

Johnson signed a five-year, $36.25 million contract extension on Monday with the Bills, a week before he was set to become an unrestricted free agent.

“I want to do all I can to make sure and let them know they didn’t make a mistake,” Johnson said. “I want to make sure they look good. This is where I started, and I wanted to remain loyal to them.”

Johnson, 25, was all smiles after he signed the deal that will keep him reunited with quarterback Ryan Fitzpatrick. The two have developed a strong relationship, and are viewed as a key cog in the Bills’ youth movement.

“I’m fired up,” Fitzpatrick said in a conference call on Monday. “This shows a lot about Stevie, and this shows a lot about where the Bills are headed. Being our go-to guy in the receiving corps and being a huge playmaker for us, it was a must in terms of re-signing him.”

Bills general manager Buddy Nix was also happy to have signed his No. 1 receiver on the last day for teams to designate prospective free agents with the franchise tag. Applying the tag on Johnson would have cost the Bills about $9.4 million next season.

“It’s a good day for us,” he said. “Our football team got better. One of our philosophies coming in is that we wanted to keep our good players here. We were able to do that with Steve Johnson. It goes without saying what he’s done the past two years, and I think it’s just going to get better.”

After being selected in the seventh round of the 2008 draft, Johnson emerged in 2010 when he led the Bills with a career-high 82 catches for 1,073 yards and 10 touchdowns. He followed that up this past season with 76 receptions, and became the first player in team history to record consecutive 1,000-yard receiving campaigns.

He has 170 catches for 2,189 yards and 19 touchdowns in 48 games during his four-year career.

The Bills would have been dealt a big blow had they not re-signed Johnson. Perennially one of the worst offensive teams in the league, they began making strides last year in Fitzpatrick’s second year as the starting quarterback. Buffalo finished 14th in the NFL in yards gained, its best ranking since finishing 11th in 2002 under the direction of quarterback Drew Bledsoe.

Johnson has been a big part of that resurgence.

“We’ve developed a great relationship,” said Fitzpatrick, who signed a six-year, $59 million contract extension in October. “To be able to continue that and see that grow for the next few years is going to be great. Chan (Gailey) and Buddy have a plan in place and this shows that we’re on the right track. We’re going to keep the guys that perform, and continue upon what we’ve done.”

Johnson agrees that the Bills are on the right path despite losing eight of their final nine games to finish 6-10 in 2011, their 12th straight season without a postseason berth.

“This group is the only group I’ve known, so why leave now when you got guys turning that corner,” he said. “There’s a lot of promise here. We have a talented group, and I think we’ll be a team that people have to take notice with these coming years.”

This past season was a turbulent and controversial one for Johnson. He fought through injuries to his shoulder, groin, and hand, and also landed in hot water for his over-the-top celebrations. He was benched for the final three quarters of the Bills’ finale at New England after being flagged a second time in six games — and third time in two years — for an excessive touchdown celebration.

But Fitzpatrick believes Johnson will leave the past behind as the two focus on taking their team to the next level.

“All the stuff with the celebrations and the penalties that happened last year — that stuff’s all done with,” Fitzpatrick said. “He’s a leader on this team, and he’s a guy that is concerned with the team and winning, and I think he’ll show that.”