An F – that’s the grade that the Boston Celtics earned last week. With an opportunity to separate themselves from the rest of the NBA’s elite, the Celtics failed, withering down the stretch of two crucial games against the best the West has to offer.More importantly, the losses came at home, at the Garden; a place where the Celtics were once nearly unbeatable.Celtics coach Doc Rivers, always the eternal optimist, tried to put a positive spin on the Celtics’ recent stretch.”Well, it tells me that we’re really good, because we’ve not played with our A-game and we still had a chance to win both,” Rivers said. “Both games, we had the lead. And gave it up. Gave up points, which is not like us. In a sick way, I guess, I’d rather be down and not be able to score than up and give up baskets, because we’re a defensive team. You know what I’m saying. But we clearly have to improve.”Celtics star Kevin Garnett doesn’t think it is time to hit the panic button just yet.”I don’t think, as a team, we’ve hit a panic button or anything like that, but it shows that we definitely have some room for improvement,” Garnett said. “Coming down the stretch, execution can be one of the things we stress.”With the All-Star break just about upon us, that can mean only one thing for the Celtics – their annual mid-February trek out West. This year’s trip does not bring any gimmies when games include Western Conference contenders New Orleans, Dallas, Utah, Phoenix, and Denver. With the fight for home court advantage in the playoffs heating up, Paul Pierce knows that the Celtics better get their act together quickly.”Now we have a tough task in front of us, going out on the road for the next couple of weeks to try and make up some more ground,” Pierce said.With only two games separating the top three teams in the league, this week’s losses could loom large in just a few short months.Tough news out of Minnesota this week. With Kevin McHale’s Timberwolves playing their best basketball since the Garnett trade, thanks to their best player, Al Jefferson, “Big Al” suffered a season-ending knee injury, tearing his ACL.McHale’s protégé was having his finest season as a professional, averaging 23 points and 11 rebounds per game. For the young Timberwolves, the loss of Jefferson is being felt both on and off the court.”We’ll miss Al in every aspect, from his personality to his play to his presence to everything else,” McHale said. “He’s such a good kid. Your heart goes out to the kid.”