The San Francisco 49ers blew a career day from quarterback Alex Smith, more opportunities to win than they could have wished for _ and a chance to keep pressure on Arizona in the NFC West.

Olindo Mare kicked a 30-yard field goal as time expired to send the Seattle Seahawks to a 20-17 victory on Sunday over inopportune and angry San Francisco.

After the 49ers called timeout to try to ice the veteran on a cold day, Mare made his second field goal of the final quarter and extended his team record of 18 consecutive makes for the Seahawks (5-7). They also kept alive hopes for a winning season, if not a playoff berth.

The Seahawks also severely damaged the postseason hopes of San Francisco (5-7).

Smith, who had never had a 300-yard passing day in his first 38 NFL games, threw for a career-high 310 yards in the 49ers' new spread offense. The No. 1 overall pick in 2005, reinstalled as San Francisco's starter in October, completed 27 of 45 throws and had two touchdown passes.

One was to Vernon Davis, who had six catches for a career-high 111 yards. Davis' 10th touchdown of the season set a single-season record for a 49ers tight end.

Yet San Francisco will regret its blown chances: two incompletions from the Seahawks 1 in the opening quarter; a fumble on punt reverse; another fumble by Gore at Seattle 22; and an ill-timed three-and-out in the final minute that left Seattle time and field position for the winning drive.

The final quarter was full of misfires by both teams, epitomizing the mild, mild West.

Four consecutive completions by Hasselbeck, three to T.J. Houshmandzadeh got Seattle to the San Francisco 40 with 1:19 left. Then came the game's fourth negative-yardage completion, a screen pass to Julius Jones destroyed by Patrick Willis for a 5-yard loss. A false-start foul by center Chris Spencer pushed Seattle back to midfield for a third-and-19 with 1:03 left. Hasselbeck lofted a perfect throw in stride into Deion Branch's arms at the 49ers 12, but the ball skidded through his hands.

Hasselbeck bent over in disbelief, and Seattle punted for the 10th time.

But the 49ers went three-passes-and-out from their own 11 _ the last pass would have been an interception by Deon Grant at midfield had he not dropped it.

Nate Burleson returned the ensuing punt 21 yards to the Seattle 48 with 21 seconds to go. Two plays later, rookie Deon Butler ran past cornerback Keith Smith and Hasselbeck's laser pass hit him in stride for a 32-yard gain. One run later, Seattle called timeout, and Mare calmly made 21st field goal in 23 tries this season as holder Jon Ryan and then the rest of the Seahawks mobbed him on the field.