Just got done watching the Utd game in full (was mostly watching the race on Sunday at the time).
I wouldn't say Utd were mesmerising going forwards at all. They lacked pace, direction, cohesion. They scored a couple nice goals but a huge majority of their attacking play was listless crap. Di Maria was the only one really driving forwards with the ball. Rooney kept roaming everywhere getting the pass then usually passing backwards again, he had the odd good moment pushing towards the opposition goal one of which created the goal but his willingness/ability to pass forwards hurts the team badly. He really so obviously wants to be a play maker but isn't good at it.
The three man narrow midfield was awful, there was no sensible idea of who should mark who, who should drop wide to help the fullback and when someone drops wide to help where they should stand in midfield and what they should do defensively.
fitness also appears to be an issue, Leicester did have multiple chances to score and lots of good counters in the first half but the second half Utd just got worse and worse. Di Maria was tiring but so was just about everyone else. Blind, Falcao, Rojo, Rafael have all barely played though Rafael was one of the few who for me was very good all game long but he was pretty much the only defender playing in position who has played in that position for years. SO many times they ran the overlap on a fullback and the midfielders weren't tracking the run the second player made leaving the fullback screwed, even then Rafael did well.
Blackett..... was god awful at every moment throughout the game. From the penalty he conceded which was stupid to the absolutely pathetic attempt to win the ball seconds earlier, painfully weak attempt to fight the ball to win the header. His positioning for every goal is awful, he is frequently tempted to run out of the back line to follow someone he thinks might get the ball but left a gaping hole every time and was slow to get back. His starting position on almost every counter attack was horrendous. For the 4th goal he didn't look behind him and was running at Laet's pace watching what he was doing, utterly oblivious to the guy running in behind him. He should be ignoring Laet and matching the guy running through the middle. Blind, Smalling and Rooney could all have dropped 10 yards deeper than they stopped as the ball came out of the Leicester box but all reacted like they'd definitely get the ball back. If they'd all dropped 10 yards further back(and all had more than enough time to do so) they'd not have conceded.
The mistakes got worse as they clearly got more tired but Blackett was woeful throughout, Smalling wasn't great after he came on, Evans has been poor, Rafael as said was the only player who performed over the entire game.
Falcao had moments, his cross was great but a lot of poor touches, some good movement though, he needs games. Rooney was meh throughout, RVP should have scored at least one more. Di Maria was generally good, Herrera/Blind/Di Maria with Rooney also helping just have no idea where they are supposed to be defensively.
Defensively they need to be at least trying two of Rojo, Smalling and Jones with Shaw and Rafael. They need to sort out what they are doing with the midfield when they are defending, who goes where and what time because currently they are all over the place. Offensively Falcao needs games and Rooney can't play that no.10 type role.
Leicester have been extremely impressive in every game so far. They are exceptionally willing to counter attack at every opportunity, they use pace and don't over commit numbers forward. Just 3-4 players all running full pace which gets the defence back peddling and losing track of where everyone is. Pretty much every team has played into their hands so far, expecting a weak team, playing possession football, getting held up around the box and not getting back or leaving enough people back to cope with their counter attacking. Unlucky not to have several more points than they do. Solid enough at the back, well organised and great on the counter. Can't see a single problem with them staying up, wouldn't be remotely surprised by a top half finish.