With one obligatory walk-through left before the Super Bowl, the Baltimore Ravens are operating at peak efficiency as they draw closer to Sunday's game against the San Francisco 49ers.The Ravens breezed through a 65-minute practice session Friday, and afterward coach John Harbaugh could barely contain his enthusiasm.Asked for his review of the practice week, Harbaugh said: "It was an A-plus. A-plus-plus. We're at the stage where we're clicking on all cylinders and practicing very, very well. "He acknowledged that there were a few assignment errors, but said they were quickly corrected.After Saturday's walk-through, linebacker Ray Lewis will walk of the practice field for the final time. He will retire after Sunday's game."I didn't even think of it," Harbaugh said before boarding the bus for the 15-minute trip back to Baltimore's team hotel in downtown New Orleans. "That's not where Ray's head is either, I'm sure. He's thinking about the game. We all are."All 53 players on the active roster participated in Friday's session, which was held at the Saints' training facility.After practice, Harbaugh gathered the team at midfield and thanked them, he said, "for how hard they've worked both this week and this season, and for who they are."He asked the players to make sure to get enough rest before the game."Family, we love them, but they're not playing in the game," he said. "Only the players are, and they need to be at their best Sunday at 6:30."