Manchester United signed Cristiano Ronaldo for the second time during the summer transfer window. The Portuguese was met with much fanfare after leaving Juventus to seal a sensational return to the Premier League.Ronaldo has wasted no time in making his impact felt at Old Trafford. The five-time Ballon d'Or winner continues with his exploits in front of goal, having bagged nine goals for the Red Devils across all competitions this season.Despite scoring consistently for the team, the attacker's arrival has failed to make Manchester United a better team. On a sincere note, the Red Devils have drifted backwards since signing Cristiano Ronaldo.That has forced many into questioning whether his signing was the right move in the first place.Goal@goalCristiano Ronaldo's worst-ever home defeat.Lionel Messi's worst league start in 16 years.The 🐐s are going through it right now 😞3:22 PM · Oct 25, 2021263292430Cristiano Ronaldo's worst-ever home defeat.Lionel Messi's worst league start in 16 years.The 🐐s are going through it right now 😞 https://t.co/ccAcLAGtGiThe warning signs were there from the beginning. It was obvious that Manchester United simply hijacked the attacker's transfer to Manchester City just to prove a point to their neighbors.Cristiano Ronaldo's signing was totally unnecessary considering the attacking options present at Old Trafford and the fact that the Red Devils had many gaping holes to fill.In fact, it would've made more sense to sign any of the five players highlighted below instead:#5 Declan RiceThe West Ham midfielder is firing on all cylinders right nowIt was quite glaring that Manchester United needed to sign a defensive midfielder during the summer transfer window. The Red Devils were linked with multiple options, including West Ham's Declan Rice.However, their plans changed immediately after they entered the race for Cristiano Ronaldo's signature.Man United News@ManUtdMENManchester United's Declan Rice transfer mistake was highlighted by Man City manchestereveningnews.co.uk/sport/football…6:19 PM · Nov 9, 2021683Manchester United's Declan Rice transfer mistake was highlighted by Man City manchestereveningnews.co.uk/sport/football…They've suffered from that poor decision this season and are now desperately in need of a reliable option to shield the defense. Declan Rice would've been a great option in that role.The Englishman is arguably the best defensive midfielder in the Premier League right now. He can even play as a third centre-back if the situation calls for it.#4 Kieran TrippierAnother option Manchester United could've signed instead of Cristiano RonaldoOle Gunnar Solskjaer recently tried playing three men at the back but the system hasn't come out very well due to the lack of players who could execute it perfectly.One such player is Atletico Madrid defender Kieran Trippier, thanks to his ability to impress in attack, just as much as he does in defense.The 31-year-old is looking to return to England and would've definitely hopped on the opportunity to join the Red Devils over the summer. Trippier is no stranger to the Premier League.He has a record of 107 appearances to his name in the English top flight, representing the likes of Burnley and Tottenham Hotspur.