SANTA CLARA (AP) — When Alex Smith is good he can be very good. When Smith is very good, the San Francisco 49ers are practically unbeatable.
While the staples of San Francisco's success this season remain a rock-solid defense and the NFL's top-ranked rushing game, Smith's play at quarterback has been a key variable that's put the 49ers over the top in a string of lopsided victories.
The first-place 49ers, coming off a bye week, begin the second half of the season Sunday against the St. Louis Rams at 6-2 with a 1½-game lead in the NFC West. The six victories have come by an average margin of 20 points, and Smith has a 120.0 quarterback rating in those games.
The eighth-year veteran knows his strong season to this point will ultimately be judged by what he and the 49ers do the remainder of the year.
Smith says he's "not really reflecting" on a first half that has established him as one of the league's top performers so far. Smith ranks fourth among NFL quarterbacks with a passer rating of 102.1. He's second in the league with a completion percentage of 69.4.
"You hope you're playing your best football come November and December," Smith said. "As you move into the back half of the season, these are huge games, so you hope you're playing better and better as the season goes on."
Smith is playing some of the best football of his career. He has steadily emerged beyond the "game-manager" label some tagged him with last season when he guided the 49ers to a 13-3 record and berth in the NFC Championship game in coach Jim Harbaugh's first year with the team.
Smith has developed more as a playmaker and is averaging 7.9 yards per pass attempt, which ranks fourth in the NFL. And he enters the second half on a roll, having produced two of the best statistical games of his career in the past month.
Smith threw for a season-high 303 yards with a passer rating of 156.3 while leading the 49ers to a franchise-record 621 yards during a 45-3 blowout of the Buffalo Bills on Oct. 7. He topped that with a career-high 157.1 passer rating in San Francisco's last game, a 24-3 victory at Arizona on Oct. 29.
Smith completed 18 of 19 passes for 232 yards and three touchdowns against the Cardinals, setting an NFL record with a 94.7 completion percentage for a quarterback with a minimum of 15 attempts. He was named NFC Offensive Player of the Week for the first time two days later.
The 49ers will complete a run of three consecutive games against their West rivals when they face the Rams, who are well aware of Smith's progress: He had two of his best games last season in wins over St. Louis.
"You have a quarterback that is playing great football," Rams linebacker James Laurinaitis said. "When you look at the Niners, they definitely have a guy who can carry them when needed. I think Alex Smith has proved that."
The 49ers have diversified their offense this season, adding veteran receivers Randy Moss and Mario Manningham to the mix. Smith's versatility allows offensive coordinator Greg Roman a lot of flexibility when determining how to come at opponents.
San Francisco has been striving for balance against opponents that key on three-time Pro Bowl running back Frank Gore and the power rushing attack the offense revolves around.
"We present a lot," said Smith, who has completions to 11 different players this season and also has rushed for 129 yards. "I love getting everybody involved, that's for sure. I feel like we're not predictable. I don't feel like (opponents) are out there knowing what we're doing. We do a lot. We run all the schemes that are there, and it's fun."
Smith's consistency and efficiency also have helped in San Francisco's climb to 13th in the NFL rankings for total offense this week after finishing 26th in that category last season.
And now, his name is being mentioned next to Joe Montana and Steve Young, the Hall of Famers who preceded Smith as San Francisco's quarterback.
If Smith's midseason numbers hold until the end of the year, his completion percentage would rank third in team history behind only Young (70.3 in 1994) and Montana (70.2 in 1989). Smith also could join Young and Montana as the only 49ers to post a quarterback rating of 100.0 or better in a season.