Nothing helps out a defense like having a big eraser in the middle to take care of business. Xavier had about the exact opposite of that effect as a team last season. The Muskies blocked 8.3% of opponents' two-point attempts, good for 231st in the country. Part of this was because of the team's defensive philosophy of walling up opposing posts rather than leaving feet to challenge shots, but a lot has to do with the fact that Xavier's big men just weren't that good at blocking shots.
What are we losing?
Dee Davis blocked two shots in four years.
Matt Stainbrook was actually a decent shot blocker, third among regulars with a block% of 2.9%. He was capable of getting to the odd attempt coming off a player's hand, but he was not the kind of rim protector you envision when you use the phrase.
Can we replace it?
Yes, and fairly simply. James Farr and Jalen Reynolds each blocked more than 5.5% of opponents' two-point attempts, which is not bad if not exactly dominant. Makinde London is an athletic and long big man; he'll be good for some weak side rim protection, though his lack of bulk keeps him from being a true one-on-one post defender. Sean O'Mara was a decent shotblocker in limited time last year; we'll see how that develops.
Blocking shots is not a big part of Xavier's defensive philosophy; they're basically just gravy whenever they happen. For all that Matt Stainbrook offered, turning away opponents at the rim wasn't part of that package.