The Boston Celtics haven't exactly had a banner offseason, losing both Al Horford and Kyrie Irving as well as depth pieces like Marcus Morris, Terry Rozier and Aron Baynes.

Yes, the Celtics signed Kemba Walker to make up for the loss of Irving and added some bulk to their front-court by landing Enes Kanter, but you can't deny that this has been a rather disappointing offseason for Boston overall.

The Celtics will still likely be one of the top teams in the Eastern Conference next season, as youngsters like Jayson Tatum and Jaylen Brown seem poised to take steps forward and Gordon Hayward should be better, but there are still plenty of question marks for this C's squad.

Here are three questions remaining for Boston after free agency.

3. Will the Other Youngsters Step Up?

By “other” youngsters, I'm talking about guys like Robert Williams and rookies Romeo Langford, Grant Williams, and Carsen Edwards; not Tatum, Brown, and Marcus Smart.

We know Tatum and Brown are going to produce, and we also know exactly what Smart, a First-Team All-Defender, brings to the table. But the biggest key to the Celtics' 2019-20 campaign could be how much they get from the rest of their young core.

Robert Williams actually got some experience this past year and looked really good, so Boston is expecting big things from him, especially in the wake of the Celtics' entire front-court being decimated this summer. Yes, Edwards looked terrific in Summer League, but that's Summer League, so it remains to be seen if that will carry over into the season.

Basically, the C's are going to need at least two of those guys to come up big next season.

2. Do the Celtics Have Enough Depth?

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The most impressive part of Boston heading into this past season was its ridiculously impressive depth, as the C's boasted what was almost surely the deepest team in the league, top to bottom.

But with all of the losses the Celtics have suffered this summer, that depth is basically gone, and now, Smart is really Boston's only truly reliable reserve, with Daniel Theis, who was at the end of the bench this past season, likely representing the second guy off the pine at the moment.

I guess this can kind of be a second part to point No. 3 above, as the Celtics will be forced to depend on some of their young and unproven talent, but that is a scary prospect, especially considering that injuries do tend to happen over the course of an 82-game season.

Depth has not really been an issue for Boston at all throughout the last decade, so this is certainly uncharted territory.

1. How Good Will the Front-Court Defense Be?

A huge strength of the C's the last couple of years was their front-court defense, as Horford and Baynes represented arguably the best one-two defensive punch at center in basketball, and Morris was no slouch either due to his versatility.

But now, the Celtics will be relying on Kanter, who is one of the worst defensive bigs in the league, Theis and a couple of neophytes in the Williamses.

The good news is that Theis is a solid defender, and Robert Williams has ridiculous potential on that end of the floor. The problem is, there are a ton of question marks here, and a whole lot of its and buts.

If the Celtics' front-court isn't able to play at least adequate defense, nothing else the team does will really matter.