The Boston Celtics are about to completely make over their roster this summer, as Kyrie Irving and Al Horford seem to be surefire goners, Aron Baynes was traded and the Celtics will also have to renounce rights to Marcus Morris and Terry Rozier in order to clear enough cap room to sign Kemba Walker, which seems to be a foregone conclusion at this point.

While signing Walker would certainly be great and would provide Boston with a very similar player to Irving without the locker room headache, the C's are going to be missing the depth that had people salivating at the beginning of last season.

Not only that, but aside from second-year big Robert Williams and rookie Grant Williams, the Celtics have nothing in their frontcourt, and this is after Boston had one of the deepest frontlines in the league the last two years.

If the C's sign Walker, they will only have the MLE to sign a big, so here are three affordable frontcourt options for the Celtics this summer:

3. Enes Kanter

Here is the thing with Enes Kanter: he can't defend in space and he can't spread the floor, but he is a great rebounder and can bang in the post, and in a division that houses Joel Embiid, that's important.

Kanter played very well for the Portland Trail Blazers this season after being picked up off waivers, and while you certainly can't play him big minutes in certain matchups, he is productive enough where he can be a starting center on a contender.

Is he the best option for the Celtics? No, but given that they already have a hyper-athletic big man in the aforementioned Robert Williams, Kanter would be a good change-of-pace center.

2. Thomas Bryant

Thomas Bryant is a very interesting player who certainly isn't a household name.

He had a solid year for the Washington Wizards this past year, averaging 10.5 points and 6.3 rebounds over 20.8 minutes per game while shooting 61.6 percent from the floor and 78.1 percent from the free-throw line.

There are a couple of catches, though: first of all, he is a restricted free agent, and at 21 years old and coming off that type of year, the Wizards should match any offer. Second, he is similar to Robert Williams in that he is long and athletic but is somewhat slight, so larger centers can push him around.

Now, he is still just a kid and can easily grow into his frame, but the Celtics need some bulk up front. Plus, given his potential, it's probably not incredibly realistic anyway, although there has been some chatter that Boston is interested in Bryant.

1. Robin Lopez

This seems like the most natural fit.

Robin Lopez is a seasoned veteran who is not great at anything but is solid at pretty much everything. He is a great finisher, a good offensive rebounder, he has a decent mid-range jumper, he can defend the post and he isn't a terrible pick-and-roll defender.

Most importantly, at seven feet tall and with solid strength, he can represent a fine option to defend bigs like Embiid. That is really the key here, as the Celtics lost that by trading Baynes.

Also, Lopez is an outstanding locker room presence, something the Celtics obviously need after such a rough year of dysfunction.