They ended up losing to the better team (the cardinals) but the statement was made. And Singletary's philosophy is one of physicality, which resonates in the NFL. There are enough athletes all around to supply every team. There are so many college athletes, semi-pros, practice team players, NFL Europe, etc., that the difference between players is small.
So what makes the difference? Motivation and effort. Which manifests itself mostly through physical play and practice preparation/weight room time.
But mostly through inspired physical play. Its also in San Francisco's favor that his message is hitting the troops half way through the season, renewing his emphasis at a time when other teams are lagging as they get burned out. Like the Browns, who allegedly quit on their own team during the loss to the Broncos.
There was also the question of poor time management at the end of the game. Well, you win some you lose some. Only the most elite coaches can do everything.