Paul Pierce is in his seventh season playing alongside Kevin Garnett, teammates since the Celtics traded for Garnett and Ray Allen in the summer of 2007. And they’ve been friends since the two of them were in high school. So if anyone could identify the cause of Garnett’s rough start this season, it’s his longtime pal. On Monday, Pierce said he thinks Garnett still will need more time to get used to his new surroundings. “I think he’s still trying to make the adjustment,” Pierce said after the Nets practiced at Fort Hamilton in Brooklyn as part of spending their Veterans Day with the troops there. “Kevin’s been one that’s always … he’s always been a guy that needed to feel comfortable, who needed to make an adjustment, the familiarity. And I think he’s still getting familiar with the offense and understanding where his shots are going to come from, the minutes played adjustment. “Even over the past four or five years, it’s been an adjustment each and every year. Even on the Celtics, because the older he’s gotten his minutes have gone down and he’s been asked to do less. … He’s going to find his rhythm eventually and really find his groove.” Garnett is famously resistant to change, and had to be sold on coming to Brooklyn by Pierce, Nets coach Jason Kidd and Deron Williams after the Nets and Celtics hashed out the draft-night trade. But after finally relenting and agreeing to join Pierce and Jason Terry with the Nets, it has been a struggle for the future Hall of Famer so far this season. Garnett is shooting 32.1 percent from the field — including just 3-for-8 (37.5 percent) on shots less than 5 feet from the basket, and 5-for-21 (23.8 percent) on shots from 14 feet and in. Last year, for example, Garnett shot 64 percent on shots from inside of 5 feet, and 53.7 percent on shots within 14 feet.