Bailly and Lindelof look like second-fiddle defenders.
United needed one or two authoritative new centre-backs.
Manchester United defence is currently 'not good enough', according to club legend Gary Neville.
Jose Mourinho's Reds lost 3-2 at Brighton in their second game of the 2018-19 season and following the defeat, the former United captain, who won a total of 20 trophies, including eight Premier League titles and two Champions League titles, explained why their defence isn't good enough to win the title.
The football expert told Sky Sports: "What Manchester United had to do, particularly in these first two games against Brighton and Leicester, was win.
"Any defeat against these two teams, especially in the way they have been beaten today, then as I said before the first game, the dark clouds that were circling over Old Trafford were going to open and burst.
"There's no doubt that before the first game of the season, Manchester United needed one or two authoritative new centre-backs.
"Jose Mourinho, in his own words, gave the list, and it wasn't delivered. For whatever reason - maybe they were too expensive, they didn't fit the club's philosophy or players weren't available.
"You knew full well that once Manchester United hadn't signed those players that the current centre-backs were going to be under big, big pressure.
"There's nothing worse for a player in a dressing room than having the club in public talking about players they haven't got and players they want to bring in in certain positions."
He continued: "What does that do to the confidence of the players who are at the club? Not a lot. What we've seen today are two players in Eric Bailly and Victor Lindelof who are lacking confidence a little bit or maybe they aren't quite good enough. Maybe the answer lies somewhere in between.
"To me, they look like second-fiddle centre-backs. If they had, for instance, John Terry, Jaap Stam, Rio Ferdinand or Nemanja Vidic alongside them then they would probably be alright.
"I call myself a second-fiddle centre-back, if that. I played a lot of games at centre-back for Manchester United, but I needed someone alongside me of real stature and strength - and a full-back of stature and strength alongside me - or else it was very difficult for me because of my lack of physicality.
"You can get messed around a little bit and those two centre-backs today for Manchester United got messed around. It happens quite a bit.
"I'm not making excuses for them. There has been £120m of investment in that back four. You've probably got the best goalkeeper in the world, so from a back-five point of view, you could argue there has been serious investment.
"However, they are not good enough. Collectively they are not good enough and individually they are not good enough."