Ryan Burnett Loses to Nonito Donaire After Retiring with Back Injury

Ryan Burnett lost the WBA unified bantamweight title after he was forced to retire ahead of Round 5 bell because of an apparent back injury suffered against Nonito Donaire in the Season 2 quarter-finals of the World Boxing Super Series in Glasgow, Scotland, on Saturday.

Burnett had to take a knee during the fourth round and then couldn't carry on ahead of the fifth at the SSE Hydro Arena. Donaire will face WBO bantamweight title-holder Zolani Tete in the semi-finals to determine the Muhammad Ali Trophy winner.

Donaire showed sympathy for Burnett after the decision was confirmed:

The extent of the injury saw the fallen champion treated immediately:

Meanwhile, some were left to rue the implications of Burnett's injury:

Back problems stopped Burnett just as the intense bout was gathering pace. Each fighter traded rounds after cagey opening exchanges.

The second belonged to Burnett, who moved well and landed telling body shots. Donaire rallied in the third by connecting with a few clean rights to the head, despite Burnett's best attempts to duck and weave beyond his more experienced opponent's reach.

As the senior fighter, the 35-year-old Donaire began to box a smarter match. He picked his shots well and tried to pick off Burnett with his jab to set him up for bigger punches.

Disaster befell Burnett in the next round as he tried to launch a precise right to break down Donaire's defenses. ESPN's Dan Rafael was among those who could find little difference between the fighters before injury struck:

Donaire has added to his decorated career haul of titles. A champion at four weights, he's left to relish the prospect of taking on Tete in the semi-finals:

Meanwhile, the 26-year-old Burnett will hope to recover quickly and regain his place as a promising talent.