Forget Kevin Garnett. The Celtics could use some Jared Sullinger right now. Confronted by a young and inconsistent, but brawny Detroit Pistons team, the Celtics were bullied in every aspect save for the final score in last night’s 98-93 victory at the Garden. The C’s were at a loss to keep Greg Monroe (24 points, 17 boards) away from the rim and outscored in the paint, 58-28. They suffered a 52-34 undressing in the rebounding battle, gave up 25 offensive boards, took 22 fewer shots (93-71) than the Pistons and yet somehow ended up with the ball and the lead with 12.8 seconds left. The Pistons had no choice but to foul Jason Terry, who hit both free throws for yet another threadbare win in a season full of them. The win, combined with Philadelphia’s loss to Charlotte, clinched the Celtics’ sixth straight playoff appearance. The C’s survival, yet again, came from Jeff Green’s evolving willingness to take charge. With a relatively quiet Paul Pierce back from a one-game absence to celebrate the birth of his third child, a son, Green sprung for 34 points (including three 3-pointers), six rebounds and four blocks. The combination of Green at small forward and Pierce at shooting guard is starting to look good enough, in fact, that coach Doc Rivers may keep the combination intact once Garnett (ankle) returns at some point over the last two weeks of the season. “It’s amazing. We’ve practiced it all year, but Jeff wasn’t ready defensively, honestly,” Rivers said of the “big” lineup pairing. “I like that lineup, though.” In a closer’s role that seems to fit Green a little better each night, he also scored all 11 of the Celtics’ points that led to Terry’s two free throws. It admittedly hasn’t been easy for Green to exert his ego on the team of Garnett, Pierce and (Rajon) Rondo, but in the vacuum created by this season’s injuries, the process is no longer a forced march. “That was the tough part, finding my groove, finding a good rhythm,” Green said of his season-long process of fitting in. “Now I’m in a good rhythm, picking and choosing when to drive and when to pull up for the 3. If (Garnett) was here I’d continue to be aggressive, and he’d tell me that, too. The more I continue to be aggressive, the more pressure that’s off of Kevin, Paul, Brandon (Bass) and Avery (Bradley). “I’m playing off of (Pierce). We’re looking for each other. If the ball is in my hands I try to make a play, and if it’s in his so will he. Teams have to make a decision on how to play us.”