Manchester United have reportedly ruled out signing David Alaba.Alaba is without a club following his release from Real Madrid at the end of last season.Alaba departed Real having made 132 appearances for the clubGettyGiven his free agent status, the 34-year-old presents an immediate quick fix for teams who need help at centre-back or left-back.Why has Manchester United avoided signing David Alaba?But the Red Devils, who targeted a new left-back to challenge Luke Shaw, won’t be pursuing the Austrian.According to the Manchester Evening News, United’s decision to swerve Alaba is because the club feels he has regressed.Alaba was named in UEFA’s Team of the Year in 2013, 2014 and 2015 while at Bayern Munich.He also landed a spot in LaLiga’s Team of the Season for the 2021/22 campaign as he helped Real win the Spanish top flight.However, Alaba has been blighted by injuries in recent seasons, the worst of which was a torn anterior cruciate ligament (ACL) in December 2023.Such has been Alaba’s injury woes over the last three seasons, he has missed 109 games for club and country.The 34-year-old’s fitness issues ultimately led him to play a bit-part role for Los Blancos last term as he made 16 appearances across all competitions, although he started only six of those.He did start in all four of Austria’s games at the World Cup, skippering the side to the Round of 32 where they were eliminated by eventual champions Spain.Which other left-backs did Manchester United look at in the summer?Along with United’s fears over Alaba’s physical decline, the Red Devils sought left-backs of a younger profile.Carrick will need Shaw to stay fit this season after United failed to add another left-back in the summerShutterstock EditorialNewcastle’s Lewis Hall was at the top of United’s shortlist, but the Magpies made it clear he was not for sale.Alejandro Balde and David Raum, who play for Barcelona and RB Leipzig respectively, were considered as alternative options.Despite United’s desire for a new left-back, the club did not sign one in the summer.It places a significant burden on Shaw’s shoulders to remain fit, especially given United are back in the Champions League.Shaw started in all 38 of United’s Premier League fixtures last term, but his injury history suggests that is an exception rather than the rule.The 31-year-old featured just 12 times for the Red Devils in the 24/25 campaign and 15 times the season prior due to a string of different muscle injuries.Shaw has started in all three of United’s fixtures to date this season and even bagged an assist in the club’s 2-2 draw with Everton last Sunday.