Tennessee avoided one of the biggest meltdowns in NCAA Tournament history Sunday, letting a 25-point lead slip away before two-time SEC player of the year Grant Williams scored 6 points in overtime for an 83-77 victory over Iowa.

The Volunteers (31-5) made it back to the Sweet 16 for the first time since 2016, though there were more tense moments than the Vols imagined after they ran off to a 44-19 lead in the opening half.

The biggest NCAA Tournament comeback? BYU’s 25-point rally past Iona in the First Four in 2012.

Tennessee's Lamonte Turner reacts in the first half against Iowa during a second round men's college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019(AP Photo/John Minchillo)
Tennessee’s Lamonte Turner reacts in the first half against Iowa during a second round men’s college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019(AP Photo/John Minchillo)

Tenth-seeded Iowa (23-12) nearly pulled off another one, sending it overtime tied at 71 — the first overtime game in this year’s tournament.

Williams had a pair of free throws, two jumpers, and a strip in overtime that helped the Vols pull it out and match their school record for wins in a season. He finished with 19 points and seven rebounds. Admiral Schofield scored 17 of his 19 in the Vols’ blistering first half.

Jordan Bohannon scored 18 for Iowa, which never led but managed to tie it twice after falling so far behind.

Iowa's Ryan Kriener, center, drives between Tennessee's Admiral Schofield, left, and Grant Williams in the first half during a second round men's college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/Tony Dejak)
Iowa’s Ryan Kriener, center, drives between Tennessee’s Admiral Schofield, left, and Grant Williams in the first half during a second round men’s college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/Tony Dejak)

Last year, the Volunteers lost to Loyola-Chicago in the second round. They followed it with a record season — ranked No. 1 for four weeks, a school-record 19-game winning streak, a full season in the Top 10 — and had just enough in overtime Sunday to keep it going.

BIG PICTURE

Iowa: The Hawkeyes wrapped up a turnaround season. They improved their win total by nine games and were second in the Big Ten in scoring in coach Fran McCaffrey’s ninth season. They were prone to give up a lot of points and lost three games by at least 20. The Vols fully exploited their defensive shortcomings.

Iowa's Tyler Cook, left, drives past Tennessee's Kyle Alexander in the first half during a second round men's college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)
Iowa’s Tyler Cook, left, drives past Tennessee’s Kyle Alexander in the first half during a second round men’s college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)

Tennessee: The Volunteers’ 31 wins match their total from 31-5 in 2007-08, when they went 31-5 and lost in the Sweet 16. Tennessee’s only Elite Eight appearance was in 2010.

UP NEXT

Tennessee heads to Louisville to play third-seeded Purdue on Thursday. The Boilermakers beat defending champion Villanova 87-61 on Saturday behind Carsen Edwards’ career-high 42 points.

Tennessee's Grant Williams, right, drives to the basket against Iowa's Joe Wieskamp in the first half during a second-round men's college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)
Tennessee’s Grant Williams, right, drives to the basket against Iowa’s Joe Wieskamp in the first half during a second-round men’s college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)

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Tennessee's Lamonte Turner (1) drives to the basket between Iowa's Nicholas Baer (51) and Iowa's Jordan Bohannon (3) in the first half during a second-round men's college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)
Tennessee’s Lamonte Turner (1) drives to the basket between Iowa’s Nicholas Baer (51) and Iowa’s Jordan Bohannon (3) in the first half during a second-round men’s college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)
Tennessee's Admiral Schofield (5) grabs a rebound ahead of Iowa's Joe Wieskamp (10) in the first half during a second round men's college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)
Tennessee’s Admiral Schofield (5) grabs a rebound ahead of Iowa’s Joe Wieskamp (10) in the first half during a second round men’s college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)
Tennessee's Jordan Bowden (23) drives past Iowa's Tyler Cook (25) in the first half during a second round men's college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)
Tennessee’s Jordan Bowden (23) drives past Iowa’s Tyler Cook (25) in the first half during a second round men’s college basketball game in the NCAA Tournament in Columbus, Ohio, Sunday, March 24, 2019. (AP Photo/John Minchillo)