Finding the missing piece: Defensive guards the Celtics could target on the trade market

David Butler II-USA TODAY SportsThe Celtics have a near-perfect rotation almost a quarter into the season. They’re 15-4, they’re atop the Eastern Conference standings, and they’re healthy.

They could, however, use one or two depth pieces to round out the roster and guard against injuries to starters. And while they have limited tradable assets, the best way to add to this roster remains a trade.

Who’s selling? The whole league is waiting on teams like the Chicago Bulls to decide whether they want to hit the reset button. The Toronto Raptors, Memphis Grizzlies, and Detroit Pistons all are performing worse than they had hoped, and all could be looking to shake up their rosters. Other teams like…