It's still early in the season, but it feels like the depth issue are less about a healthy latter half of the rotation (though Kornet is fairly below average for his spot in the rotation) and more at the top when injuries occur. Horford (obviously), Hauser, and PP have shown themselves to be quality bench pieces, even if not in the top tier.
When we're fully healthy - particularly the top 6 - we look unstoppable and very difficult to beat. But we're clearly not the same when missing one or more of our starters and to a lesser extent Horford. Our margin of error significantly decreases, and we have to win by playing smarter, more tactical ball, which is not our strong suit. We've clearly been missing Porzingis, who really would've helped tonight from both an offensive and defensive standpoint.