Liverpool’s first-choice shot-stopper Alisson suffered a shoulder injury in training last week and missed Sunday’s extraordinary 7-2 defeat to Aston Villa.
Alisson’s deputy, Adrian, has struggled when called upon and made another mistake as Villa stunned Jurgen Klopp’s side.
With Alisson potentially facing another six weeks out, former Tottenham manager Redknapp is surprised Liverpool have not signed another goalkeeper and says they could have targeted Romero.
Argentina international Romero has made just seven Premier League appearances for Manchester United since joining the club in 2015 and his wife slammed Ed Woodward on deadline day for preventing him from leaving.
Discussing Romero’s future on Sky Sports, Redknapp said: ‘You would have thought he might have gone to Liverpool.
‘Liverpool need a goalkeeper. They need a goalkeeper more than Everton (who were also linked with the Manchester United goalkeeper).
‘If Alisson is out for a while, it could be vital for Liverpool. They’re going to need to make sure they have good back-up because it sounds like he could be out for a long time.’
Romero played back-up to David de Gea at Old Trafford last season but Dean Henderson has moved ahead of the Argentine after returning from his loan stint at Sheffield United.
Discussing Alisson’s injury over the weekend, Liverpool manager Klopp said: ‘It was an incident in training; very unlucky.
‘We don’t know 100 per cent but he cannot play today. We have to do further assessments but he’s injured, let me say it like this. Now we hope it will go really quickly.
‘It’s an international break. I’m pretty sure after that he will not be ready, then we have to see week by week.’