John, who spent the past four seasons playing under former Duke star and assistant Steve Wojciechowski with the Golden Eagles, announced Friday that he had committed to Mike Krzyzewski and Duke.
"After conversations with my family, I have decided that next year I will be attending Duke University for my final year of eligibility," John wrote on Twitter. "I would like to thank everyone who has been a part of my basketball journey. Happy to be joining #TheBrotherHood."
John, a 6-foot-9 senior center from Minneapolis, ends his Marquette career with the second most blocked shots in program history. He has started 87 games over the past three seasons, emerging as one of the best defensive players in the Big East. This past season, he averaged 8.0 points, 5.0 rebounds and 1.5 blocks and shot 57.2% from the field.
Duke badly needed some experience and physicality up front, and John should immediately step in and provide depth down low. The Blue Devils lost forward Matthew Hurt to the NBA draft earlier this week, and reserve big man Patrick Tape entered the transfer portal last month. Freshman Mark Williams is an NBA prospect but is likely to return to Durham next season; he and John should form a formidable duo.
John was ranked No. 85 in ESPN's transfer rankings.