In a season filled with a series of ups and downs, the NBA champion Celtics can rest easy, knowing that they have an identical record (37-9) as they did last season through 46 games. However, the more interesting number is that of the numbers on the calendar, as last year’s edition of the Green did not play their 46th game until Feb. 6. With their core of players not getting any younger, and an arguably weaker bench, the Celtics are certainly looking forward to a well-deserved All-Star break in a couple of weeks.Paul Pierce admitted as such, saying, “The schedule is catching up with us. The second half of the year, when we’re not playing as many games as we did in the first half, we have more time to come out here and practice.”Although the Celtics are a veteran team, practice time is very important to avoid what coach Doc Rivers calls “slippage.” Case in point: During the Celtics’ 2-7 skid, the team only had one practice; through its recent 8-game winning streak, the Celtics have practiced nearly every other day.As the Celtics embark on the second half of the season, practice time will be of even greater importance, not only to help avoid any further “slippage,” but also to help provide a smooth transition for any new players that Danny Ainge may bring in. Remember, last season, it took P.J. Brown two months to get comfortable with the Celtics’ complicated defensive system, and some would argue that Sam Cassell never got comfortable with it at all. One of the Celtics’ most glaring holes is that of a back-up big man; the talent pool for that position took a major hit last week with the official retirement of 38-year-old Alonzo Mourning.Despite Mourning’s announcement, Ainge still has not got given up on signing the seven-time All-Star, saying “Until I move in another direction, I have still got their names on my board. I think they have retired. I believe they’re not ever going to play again. But it wouldn’t be the first time a player has changed his mind. Remember, P.J. didn’t show any interest in coming back last year until the All-Star break.”Another retired player that Ainge reached out to last week was former Pacers star and current TNT announcer Reggie Miller. This is the second time in two years Ainge has tried to lure the sharpshooter out of retirement.Whether it is to avoid any further “slippage,” or to successfully bring new players into the system, it is clear that if the Celtics plan on repeating as champions, practice will indeed make perfect.