Rapid Reaction: 49ers 25, Lions 19

DETROIT -- Thoughts on the San Francisco 49ers' 25-19 victory over the previously unbeaten Detroit Lions at Ford Field in Week 6:

What it means: The 49ers can beat a good team on the road without their best stuff. This makes them a legitimate contender in the NFC. They remain a work in progress, too. Some of the coaching decisions seemed questionable, a departure from form for Jim Harbaugh through the first five games. Alex Smith's inaccuracy resurfaced when he threw too high for Michael Crabtree more than once. But with the game on the line, Smith delivered a 6-yard scoring pass to Delanie Walker for the go-ahead points in the final two minutes. The shortcomings simply show there's room for improvement, even though the 49ers are 5-1. That's a great thing for them heading into the bye week. Count this as yet another signature victory for the 49ers under Harbaugh.

What I liked: Frank Gore found ample running room and came through with big plays when the 49ers needed them. Receiver Michael Crabtree also stepped up for the 49ers, including when he provided a 27-yard reception on third down after the teams had combined to convert only twice on 17 third-down opportunities to that point in the game. Rookie Aldon Smith continued to improve, making a huge play when he tackled Matthew Stafford in the end zone for a safety. He collected another sack and forced fumble in the fourth quarter. Linebacker Patrick Willis, although beaten for a touchdown despite very tight coverage, blanketed the Lions' tight ends and helped shut down underneath plays repeatedly. Overall, the 49ers hung tough and went back to the running game late when they needed to run time off the clock with a chance to score the go-ahead touchdown. And Alex Smith's ability to throw the winning touchdown pass in a clutch situation represented a giant step forward. David Akers' strong kicking is easy to take for granted, but without his 55-yard field goal before halftime and 37-yarder late, it's a different game.

What I didn't like: The 49ers played to the Lions' strengths early. They called a pass play to open the game, inviting trouble against a strong pass-rushing team in a noisy environment. It was no surprise, under the circumstances, when the Lions' Kyle Vanden Bosch came through with a sack and forced fumble -- exactly the type of start the 49ers needed to avoid in this environment. The crowd was immediately in the game, and the 49ers compounded the situation with false starts. Early in the second half, the 49ers invited trouble again by going with an empty backfield from their own 20-yard line, tipping off the quick pass that followed (for a 3-yard loss). The 49ers ran the ball well when they gave it to Gore, but they did not give the ball to him frequently enough. At one point in the third quarter, Gore had six carries for 121 yards. He needed more carries against a Lions defense that wasn't very strong against the run. Penalty problems persisted and were a factor in creating the unfavorable down and distance precipitating Alex Smith's interception.

Critical calls: Multiple high-impact rulings from Mike Carey's officiating crew spiced up this game. I didn't see justification for the chop-block call or horse-collar call against the Lions or the 19-yard interference penalty against 49ers cornerback Carlos Rogers. Officials initially disallowed Nate Burleson's touchdown grab for the Lions in a ruling reminiscent of the famous Calvin Johnson play against Chicago last season. Upon review, however, Carey determined that Burleson had had possession of the ball long enough before the field goal net resting along the end line dislodged the ball from the receiver's hand. Then, with the game on the line and the 49ers having scored the go-ahead touchdown on fourth-and-6, Carey took another look to see whether Walker's knee touched down before the ball crossed the goal line. Carey determined the ruling on the field would stand. Walker's left leg obscured his right knee from view on one of the critical angles.

Calvin Johnson watch: The 49ers generally did a good job against the NFL's leader in touchdown receptions until Johnson broke free for a 41-yard reception in the fourth quarter. Johnson beat Rogers off the line and gained additional yardage after free safety Dashon Goldson missed him. Linebacker NaVorro Bowman was the one to catch Johnson. Johnson finished with six receptions for 102 yards, but he went without a touchdown for the first time all season. That counts as a victory for the 49ers no matter how many yards Johnson gained.

Injuries of note: Right guard Adam Snyder left the game with a stinger. Chilo Rachal replaced him.

What's next: The 49ers have a bye.