TORONTO -- They can open and close the roof at Rogers Centre, slap a little paint and a few logos on the turf and call it an NFL game.

But detractors aren't easily fooled.

In a city where the Canadian Maple Leaf is proudly displayed and the only thing more plentiful than the traffic is the number of hockey fans, the Steelers' defense looked as though it were slipping and sliding on ice against the Buffalo Bills last night.

And it wasn't the backups and players who won't be around in September who were looking awkward and clumsy. It was the first-unit defense, the one that had trouble protecting leads last season.

"Hopefully, it's just preseason football," Steelers coach Mike Tomlin said.

But real games don't begin for a couple of weeks. And, not to worry, Lawrence Timmons will play more than he did in the first quarter -- one play -- once Sept. 7 rolls around.

Nonetheless, in two preseason outings, the first-team defense has allowed a field goal and two touchdowns on four possessions, the latest act of forgiveness coming in the 24-21 loss to the Bills.

"It wasn't anything great," inside linebacker Larry Foote said.

"We weren't at our peak," said nose tackle Casey Hampton, appearing in his first game since coming off the physically unable to perform list. "They ran the plays we knew were coming. They just were dropping the ball on us."

If it were hockey, they would have pulled the goalie.

After the Philadelphia Eagles marched down the field and kicked a field goal in their only appearance last week, the first-team defense hardly stiffened against the Bills, who scored the third-fewest points (252) in the league last season.

Buffalo scored on its first two possessions -- quarterback Trent Edwards threw touchdowns passes of 7 and 13 yards to tight end Robert Royal -- before the Steelers finally forced a three-and-out, the only one of the preseason for the first-teamers.

Granted, the defense showed almost none of its sub packages against the Bills, using cornerback William Gay as a replacement for Hampton on just five occasions and rarely blitzing. On the Bills' 10-play scoring drive that gave them a 7-0 lead, the base defense was on the field for nine plays .

"You look at a lot of what [the Bills] ran, they game-planned," safety Ryan Clark said. "We didn't game-plan. It's still the preseason. We're kind of sitting back and giving guys an opportunity to get their feet under them. Maybe next week we'll try to do a couple things to get that confidence that we can stop people."

Still, there are too many holes in the defense, and it has been this way since the second half of last season, even though the defense ranked No. 1 overall in the NFL. And many of the lapses came in the fourth quarter.

On five occasions in 2007, the defense failed to protect a lead in the final minutes after the offense rallied from deficits, some double-digit shortages. The only time it didn't result in defeat was when Cleveland's Phil Dawson missed a 52-yard field goal as time expired in Week 9.

The most serious collapse came in the playoff loss to Jacksonville , when the offense rallied from a 28-10 deficit with three touchdowns in the fourth quarter and the defense let the Jaguars go 44 yards in eight plays and kick the winning field goal with 37 seconds remaining. The tackling wasn't much better against the Bills.

On three consecutive plays on the Bills' second touchdown drive, Gay missed a tackle on wide receiver Roscoe Parrish, resulting in a first down; cornerback Ike Taylor missed a tackle on wide receiver Lee Evans, resulting in a 17-yard gain; and Clark missed a tackle on a swing pass to running back Fred Jackson, turning a loss into a 5-yard gain. For good measure, there was even a long run by the quarterback on third-and-13 -- Edwards stepping up in the pocket from his own 7 and gaining 22 yards to keep a scoring drive alive.

"The tackling was not up to snuff," Tomlin said. "We got to get better tackling than we are at this point."