When San Francisco and New York met in January with a Super Bowl berth on the line, the 49ers committed crucial turnovers and their offense couldn't do much against the Giants' stingy defense.

A similar performance seems unlikely in Sunday's NFC championship game rematch, considering Alex Smith and the 49ers are coming off one of the most impressive offensive showings in NFL history and the Giants are struggling defensively.

San Francisco (4-1) has been eagerly awaiting this game after New York won 20-17 in overtime at Candlestick Park on Jan. 22, costing the 49ers a trip to the Super Bowl. The loss was especially disheartening given that Kyle Williams muffed two punt returns -- one in the fourth quarter leading to a touchdown and another in OT setting up the Giants' winning field goal -- and Michael Crabtree's catch for three yards was the lone reception by a San Francisco receiver.

"Of course after what happened last year I definitely want to get back at these guys," Williams said. "We look at it as if they have something that we should have had. We're going to make sure we don't leave anything on the field again."

San Francisco hasn't had that problem lately, outscoring its last two opponents 79-3.

The 49ers are tied for third in the NFL in scoring with an average of 29.8 points, and they became the first team in league history with 300 yards passing and 300 yards rushing in the same game while gaining a franchise-record 621 yards in last Sunday's 45-3 win over Buffalo.

"The talent level has been upgraded," coach Jim Harbaugh said.

Smith, who sprained his middle finger against the Bills but said it wasn't an issue, has the league's best passer rating at 108.7. The receiving corps, with a boost from offseason additions Randy Moss and former Giant Mario Manningham, is averaging 11.8 catches.

"We had a whole offseason to work together," Williams said. "I think we're more polished than anything. We have more weapons. We added a few guys and they have helped us tremendously this year."

The Giants (3-2) have been just as impressive offensively, ranking second in both total yards with an average of 429.2 and scoring with 30.4 points per game. They've amassed 1,877 yards in the last four weeks -- their most over a four-game stretch in franchise history -- and in last Sunday's 41-27 win over Cleveland, Ahmad Bradshaw and Victor Cruz became the first teammates to rush for 200 yards and catch three TD passes in a game since 1960.

"The Giants are an outstanding team," Harbaugh said. "They've got an explosive offense. They're very balanced."

One thing they don't have right now is a reliable defense.

In last season's playoffs, New York held Green Bay (the NFL's No. 1 scoring offense), New England (No. 3), Atlanta (No. 7) and San Francisco to an average of 14.0 points. It is yielding an average of 22.2 points this year and has allowed 24 plays of at least 20 yards, sixth-worst in the NFL entering Week 6.

"We've definitely got to continue to get better as a unit," middle linebacker Chase Blackburn said. "There is no doubt we have to be better this week. We have a challenge."

New York's offense, although firing on all cylinders over the last few weeks, also seems like it will have its hands full against a San Francisco team that is allowing a league-low 13.6 points per game.

The 49ers thoroughly frustrated Eli Manning in last season's championship game, sacking him six times and hitting him on six other pass attempts, and the Giants haven't forgotten.

"That game was certainly something that we thought about all (offseason) even though we won the Super Bowl and we beat them in that game," guard Chris Snee said. "We still walked away saying that we didn't play well, we didn't do our job up front. That can motivate you though the offseason."

That has seemed to work, as Manning has been sacked just five times, giving him time to pick apart defenses.

Manning enters Week 6 second in the NFL with 1,579 yards and has 10 touchdowns. His favorite target, Cruz, has 37 receptions -- the fourth-most in the NFL -- and had 10 catches for 142 yards in last season's championship game.

His other go-to receiver also could be on his way back. Hakeem Nicks, who had the second-highest total of receiving yards (444) in postseason history during New York's latest Super Bowl run, practiced on a limited basis Thursday after missing the past three games with swelling in his left knee and pain in his right foot.

There's a chance he could play Sunday, but Nicks is wary of aggravating the injuries and missing more time.

The Giants finally got their ground game going last Sunday, as Bradshaw rushed for a career-best 200 yards after totaling 133 in his first three contests. New York is 9-0 when Bradshaw runs for at least 100 yards, but the Niners have allowed just one 100-yard rusher -- Seattle's Marshawn Lynch last December -- in their last 43 games.

Bradshaw's former teammate, running back Brandon Jacobs (knee), is questionable to make his 49ers debut against the team he spent his first seven seasons with in the NFL.

Top Niners running back Frank Gore has totaled 434 rushing yards, and his 5.5 yards per attempt ranks among the best in the league.