Kent, who also had Zak Crawley withdrawn by England, gave a debut to all-rounder Ekansh Singh, 18, among three changes while Glamorgan welcomed back experienced seamer James Harris after injury.
Glamorgan started confidently enough but Zain Ul Hassan, after hitting a couple of sweet off-drives, edged to Tawanda Muyeye at slip for 16 in Kashif Ali’s first over.
A generous helping of extras helped Glamorgan’s total from stalling, with the usually fast-scoring Tribe starting carefully as former Kent stalwart Sam Northeast played himself in serenely.
Tribe accelerated to his half-century the delivery before lunch against some inconsistent bowling, but Italy international Grant Stewart came out firing with a fine spell after lunch as he forced Northeast to edge to slip for 42 in a stand of 95.
A brilliant leaping slip catch by Daniel Bell-Drummond got rid of Kiran Carlson for 16, and leg-spinner Matt Parkinson bowled Tribe when it seemed the Jersey youngster was set for a maiden century.
Despite his disappointment, a fourth score of 50 or more in as many matches, including a healthy haul of 16 boundaries, suggests he has the technique to become established at the top of the order.
Colin Ingram was next to press the accelerator with a lofted straight six off Parkinson after one miscue just over mid-off, as he moved to 50 off just 47 balls.
He and Kellaway added 133 at four an over without undue alarm, and although Ingram slowed down in the latter stages of his knock, he was disappointed to be given out caught behind down leg-side from Kashif’s first ball with the new cherry.
Kellaway passed his previous career-best of 74 with a rare edge over the slips, although he lost Chris Cooke (15) who saw his off-stump knocked back by Kashif.
Timm van der Gugten fell for 17 in George Garrett’s last over but Kellaway was left in sight of a maiden century overnight as he and Tribe offered potential long-term promise for Glamorgan.
