SAN FRANCISCO - A rookie coach inheriting a defective team has to fully understand why his team missed the playoffs before he can fully grasp what it needs to make them.

Mike Singletary either didn't know this or refused to accept it.

Singletary is discovering where his team stands relative to the rest of the league, gaining an idea of what it has that others don't, what others have that it does not.

That's why December is the most important month of the season for so many players - and for general manager Scot McCloughan. Some of the players won't be back in 2010. And McCloughan, the man responsible for acquiring talent, is fighting to keep his job.

Assuming the 49ers, who play NFC West leader Arizona tonight at Candlestick Park, don't finish the season on a five-game losing streak, Singletary likely would be invited back, despite a choppy season.

The Eagles host the 49ers next Sunday at Lincoln Financial Field (1 p.m., Fox). San Francisco (5-7) visits Philly to face a team the 49ers have not beaten since 2003.

For months, Singletary pounded home the notion that San Francisco's identity would be as a power-run offense, with Frank Gore as the central figure.

That's changed for the 49ers since they started the season with a win at Arizona, the defending NFC champion. San Francisco has switched quarterbacks since the last meeting. Singletary promoted Alex Smith at halftime against Houston on Oct. 25. Rookie receiver Michael Crabtree had yet to sign the last time these teams played, too.

Singletary finally relented about his offense upon seeing the success Smith was having out of the shotgun and in a spread offense, with a handful of talented targets to choose from.

"We're basically trying to be a balanced team. At the beginning of the season we started out wanting to be a power-running offense but they did a great job on Frank the first game and we didn't end up doing that," receiver Josh Morgan said. "We just go how the game goes. We have the type of offense to do a lot of different things. We're adding another dimension. We're still going to have that basic power-running attack with Frank and he's going to do some big things in the run game for us."

Gore carried 22 times for only 30 yards in the first meeting with Arizona, yet he followed that up by running for a season-best 207 in a win over Seattle the following week. In his last three games, he's had seven, 16 and nine carries - for 59, 33 and 25 yards, respectively. But he's also had 15 catches during that span.

Tight end Vernon Davis has 11 touchdown catches, most in franchise history at his position. He repeatedly said he could produce this kind of big year if only given the opportunities.

With Gore and Davis and Morgan, even Crabtree, the Cardinals could have their hands full. Smith is coming off a game in which he threw for a career-high 310 yards in a loss at Seattle.

Kurt Warner shined last Sunday in beating Brett Favre and Minnesota, throwing for 285 yards and three touchdowns in the 30-17 Arizona victory. He topped the 3,000-yard mark for the season and earned NFC Offensive Player of the Week honors.

Arizona (8-4) would like nothing more than to beat its division rival wrap up the division. This team believes it can make another special postseason run after reaching the Super Bowl last season.