Think of the tallest person you know. Statistically speaking, something on the order of < 5% of the population is over 6'3", so I'm going to assume the person you're imagining is probably 6'5" at the most. Now think of the most athletic person you know. He (or she, not here to judge) can probably run pretty fast, or jump pretty high, or change direction pretty quickly. Now combine the first person's height with the second person's athletic ability. Now make him about four inches taller. Now make him even more athletic. Congratulations; you're starting to approach the freakish specimen Xavier has in Jalen Reynolds.
Reynolds's most obvious road to immediate contribution runs through his physical skills. Not only is he extremely athletic for a man his size, he also carries a good deal of strength in his upper and lower body, making him a powerful rebounder and an explosive finisher at the rim. He will turn 21 this December, so he isn't a typical freshman needing to add pounds and power to make his way through a long college season. He also has above-average ball skills for a big man, with a jumper that must be respected and the ability to put the ball on the deck to make plays when he needs to. That his athleticism plays well on the defensive end almost goes without saying, but here I am saying it anyway.
Before you get carried away, let me also point out that there are some reasons to be cautious about Reynolds's potential this year. Owing to his being a partial qualifier last season, he has not played a meaningful game in almost two years. He also was not able to even practice with the team last season, so he is going to be learning the system on the fly. Finally, there is always the potential that his style - especially after nearly two years off - is a little too rough-and-tumble for NCAA officials, though the Big East has a reputation as a league where contact is encouraged.
Best case scenario: Conference rookie of the year. Reynolds was a teammate of Semaj Christon's at Brewster Academy, and the two have enough on-court chemistry that Jalen's transition to collegiate ball is almost seamless. He can get up and down the floor when Xavier runs, but he also has the half-court skills to be a go-to scorer from the high or low post. With his ability to rebound on both ends and clean up teammates' messes on defense, he is a fixture on the court from day one and gives Coach Mack the best kind of problem trying to figure out how to balance minutes with Reynolds, Stainbrook, and Philmore.
Worst case scenario: Even with rusty ball skills, Reynolds's athletic ability plays. Adjusting to the college game at both ends of the floor takes time, and he has difficulty meshing into Xavier's half-court sets on the offensive end. Reynolds doesn't get as many minutes as one would hope, leaving the frontcourt burden to be carried mostly by Stainbrook and Philmore. Even struggling, though, a missed shot is a missed shot, and Reynolds is able to be a force on the boards and score on stickbacks. He ends the year as a 6 and 4 guy with plenty of room to make a jump next season.
Most likely scenario: I'm very high on this young man. His work ethic was well spoken-of in high school and at Brewster, and I doubt that has gone away in a year. A high motor player anyway, Jalen comes into the season with a chip on his shoulder, and his willingness to go after it on both ends plays right away. He starts the season as an energy body off the bench and sees both minutes and production steadily increase throughout the year as he grows more comfortable. I wouldn't be surprised to see him sporting averages of 10 and 6 by the time the year is out.