SANTA CLARA, Calif. -- The San Francisco 49ers have improved in just about every facet of the offense this season. But there is one area where they didn't really need to get much better.
The 49ers are protecting the football better than anybody in the NFL, and their turnover-free play is reaching historic proportions.
San Francisco hasn't committed a turnover in six consecutive regular-season games dating to last season, the second-longest streak in NFL history. The 49ers can match the league record set by the 2010 New England Patriots on Sunday night when they face the Detroit Lions.
Leading the way is quarterback Alex Smith, who hasn't thrown an interception in a franchise-record 185 consecutive regular-season passes. Smith threw just five picks last season -- the fewest in the league for a regular starter -- as San Francisco committed an NFL-low 10 turnovers.
They have not lost a fumble since tight end Vernon Davis fumbled after catching a pass from Smith in the fourth quarter of a Nov. 6 victory at Washington. The 49ers have a streak of 36 consecutive quarters without losing a fumble.
"In the history of the NFL, the strongest correlation to winning and losing is the turnover ratio," Smith said. "The turnover battle is the No. 1."
The 49ers know all about it. They finished 13-3 last season and made their first trip to the playoffs since 2002 after leading the NFL with a plus-28 turnover differential, one of the league's best since the 1970 AFL-NFL merger.
The previous seven seasons, all of which they finished without a winning record, San Francisco committed 221 turnovers and had a cumulative turnover differential of minus-57.
The 49ers changed that dramatically once Jim Harbaugh and a new coaching staff took over the team last year. San Francisco matched the NFL record for fewest turnovers in a season, also held by the 2010 Patriots.
"Ball security relates to your team being successful, and we're very serious about that," Harbaugh said.
Smith isn't the only one. Three-time Pro Bowl running back Frank Gore, who had two lost fumbles among his 299 touches last season, enters Sunday's game with a career-best string of 226 touches (220 rushes, six receptions) without a lost fumble.
Gore's backup, Kendall Hunter, has never fumbled in his 17 career games.
Harbaugh credits running backs coach Tom Rathman, who played fullback for the 49ers from 1986-1993, with "doing as good a job as any of us have ever seen done," in preparing his unit to protect the football.
Copyright 2012 by The Associated Press