For Toronto linebacker Mike Labinjo, it was a trial by fire.
For Brantford offensive lineman Nick Kaczur, it was a pleasant surprise.
Labinjo and Kaczur, who play for the Philadelphia Eagles and New England Patriots, respectively, found themselves in prominent roles in the opening week of the 2005 campaign and neither looked out of place.
Labinjo, a second-year undrafted player, was pressed into starting duty when Jeremiah Trotter was booted out of a Monday night game after a pre-game fight with the Atlanta Falcons' Kevin Mathis. Labinjo made three solo tackles.
"I was really nervous," Labinjo told the Philadelphia Daily News after the Falcons' 14-10 win. "Even after the first play, hearing that crowd. The first two series, I had trouble breathing. I was really winded. But I felt like the guys were looking to me to step up and fill Trot's shoes. Hopefully, I did a good enough job."
Of course, it's impossible for a first-time starter to perform at an all-star's level.
"It was a big difference without Trot," Eagles defensive end Jevon Kearse said. "Not to knock Labinjo. He did a great job, but he wasn't ready for that, to be thrown into the heat of the battle like that."
Kaczur, a third-round Patriots pick this year and the Argos' first pick in the CFL's Canadian college draft, subbed in regularly at left and right tackle during the Patriots' 30-20 win over the Oakland Raiders last week.
"It was really exciting, unexpected, but great," Kaczur told the Boston Globe. "I had no idea at all. Wherever they put me, that's where I play."
So far, Patriots coach Bill Belichick likes what he sees.
"I think that Nick has done enough this year in pre-season and in training camp to earn some playing time," Belichick said. "Whether that continues or doesn't continue, I don't know. That will be determined by the way he plays, the way other people play, and again, that just builds a little bit of our versatility."