Johnson signed a two-year, $24 million deal with the Celtics on Wednesday, Sam Amick of USA Today reports. The 28-year-old will accept a short-term deal with his sights set on hitting free agency again in two summers when the cap is expected to be significantly higher. Johnson averaged 9.3 points and 6.1 rebounds in 26 minutes for Toronto last season, and he'll compete for a starting spot in the Celtics' frontcourt.