The Celtics just need to play harder. If both teams play equally hard, the team with more talent will prevail.
The only reason the Sixers are in this series, and I do give them credit, is that they play hard every minute, regardless if they're up by 10 or down by 15.
If the Celtics play with the effort they do, if they play as hard as they do, it's really no contest. You can see it even in these last few minutes of this quarter.