Former Premier League defender Curtis Davies said the decision was an “absolute disgrace”.
“Kelly goes up for a header, he’s gone for the header cleanly. His feet have to land on the ground somewhere,” he added on BBC Radio 5 Live.
“Unfortunately, he lands on the player. There needs to be a level of understanding – where is he meant to put his feet? I understand Kelly’s frustration.”
Davies’ sentiments were echoed by football journalist Rory Smith, who called the decision “awful” and a “disgrace”.
Meanwhile, former Tottenham midfielder Andy Reid felt football was “moving closer and closer to being a non-contact sport”.
“There needs to be contact in football and sometimes people do get painful ones. It happens. There’s nothing you can do about that. It’s part of the game,” he said.
According to Uefa rules, any player sent off by the referee – whether that is via two yellows or a straight red – is automatically suspended for the next match in European club competition.
However, in light of Juventus’ exit from the Champions League, Kelly’s suspension will carry over to next season.
Former Manchester City defender Nedum Onuoha added: “If I was Kelly I’d be really disappointed, but with how football works, it’s always going to be a red.”
But former Liverpool full-back Stephen Warnock disagreed.
“I don’t agree with it because it is purely accidental. I understand the yellow card, but not the red,” he said.