Breaking down the latest NBA rookie contract extensions on deadline day

Jaren Jackson Jr.'s highlight-reel plays from last season (2:03)

In honor of his new contract, relive some of Jaren Jackson Jr.'s top plays from last season. (2:03)

The start of the 2021-22 NBA league year not only meant the beginning of free agency but also extensions for former first-round picks entering the fourth and final season of their rookie contracts.

The 2018 draft has provided a particularly plentiful class of rookie extensions. After Luka Doncic, Trae Young and Shai Gilgeous-Alexander all signed max extensions earlier this summer, the Boston Celtics became the first team to sign a 2018 pick to a non-max extension, locking up center Robert Williams III. And plenty more deals are getting reported ahead of today's 6 p.m. ET deadline.

Which extensions look likely to age best and which might be mistakes? Let's break them all down here.

Memphis Grizzlies

Agreed to a reported four-year, $105 million extension with forward Jaren Jackson Jr.

Gauging Jackson's value was one of the trickier questions of extension season because he missed the first 61 games of 2020-21 following surgery to repair a meniscus tear. Predictably, Jackson never got back to the form he'd shown in his second NBA season as a scorer, making just 28% of his 3-point attempts.