reports: The Celtics are grooving on defense, and it’s got them riding a nine-game streak. The Celts lead the NBA in points allowed, FG and TP percentage allowed, and rebounding differential. Boston’s PPG differential is +14.2; the diff for the second-best stoppers, the Pistons, is +7.9. The C’s sit at No. 2 and 3 in SPG and steal differential, and are the No. 1 Scrooge with dimes, allowing 17.3 per game – exactly how many they let Toronto have Sunday. The Raptors normally dish 23 APG. “The plays we usually make just weren’t there,” Chris Bosh said after the C’s 90-77 clampdown. Boston is 20-2 because it believes “stop” means “go”: “We’re trying to have the defense fuel the offense,” said Kevin Garnett, “and it’s been working.”