text: Jose Mourinho's side had applied incessant pressure on the Foxes from kick-off, and Romelu Lukaku missed a second-half penalty prior to the goals, as they found it difficult to break the steadfast backline.
  I think we frustrated them for large parts of the game
  They finally breached the last line of defence when Rashford converted Henrikh Mkhitaryan's corner three minutes after coming on.
  And then midfielder Fellaini stuck out his knee to divert fellow substitute Jesse Lingard's drive past Kasper Schmeichel.
  United are the only side to have won all three of their opening league games this season and have yet to concede a goal.
  United peppered the opposition area with crosses in the first half, but aside from a Paul Pogba strike that drifted narrowly wide, the threat from the wings was comfortably dealt with by the Foxes' defensive giants Wes Morgan and Harry Maguire.
  There was a shift in manager Mourinho's thinking in the second half as his side began to breach the 18-yard area with shorter balls from a more central position.
  That probing should have resulted in the opening goal. Leicester were once again on the back foot in their area before Anthony Martial struck a shot that came off Danny Simpson's arm. Referee Michael Oliver declared it to be deliberate handball.
  ...plus reaction & video here
  Lukaku stepped up to the spot, but his hopes of a fourth league goal this season were thwarted by Schmeichel's dive to the right.
  Leicester continued to come under pressure and eventually succumbed when Rashford's instinctive shot flew past the Dane in goal in the 70th minute.
  Holes now began to appear in Leicester's previously watertight defence as they went looking for an equaliser.
  United capitalised again as substitute Lingard's low drive was diverted into the net by Fellaini, although replays suggested the Belgian was fractionally offside.
  Leicester manager Craig Shakespeare should not be too despondent.
  His side's valiant defensive display was reminiscent of those during the Premier League-winning campaign two seasons ago. It was at the other end that his men disappointed.
  At Old Trafford, both Jamie Vardy - the Foxes' star striker of 2015-16 - and Shinji Okazaki were ineffective, while Riyad Mahrez teased the United defence without an end product.
  Vardy was withdrawn with 15 minutes left, to be replaced by Islam Slimani.
  The closest Leicester came to scoring was when substitute Andy King forced a brilliant point-blank save from David de Gea in the final few seconds of the match.
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  Manchester United manager Jose Mourinho on winning the first three matches: "We can look into perspective. Last season we won against Leicester at home so that doesn't make a difference, but we had too many draws at home last season.
  "The difference is the quality of our football, we're playing better today. If we hadn't won this match I wouldn't have anyone to blame.
  The team is playing very well and I'm very confident. We are comfortable on the ball and dangerous on the counter-attack. But nine points after three matches is nothing different for us, because we did that last season.
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  Leicester boss Craig Shakespeare: "I think we frustrated them for large parts of the game. When you come to Old Trafford in the form they are in, they will have big moments. We had our moments too, but could not see the game through.
  "Set-pieces are our Achilles heel at the moment. We need to organise better.
  "It was a harsh penalty, but a great save form Schmeichel. To go 1-0 down, it knocked a bit of spirit from us. I'm disappointed in the overall result, but we were nice and solid for large parts.
  "You have to be disciplined; you know what the opposition's strengths are. We tried to attack in the second half.
  "Maguire was carrying a knock but was desperate to play - he was solid."
  United are at Stoke on Saturday, 9 September (17:30 BST) when the Premier League resumes after the international break. Leicester are at home to Chelsea on the same day (15:00 BST).
  Match ends, Manchester United 2, Leicester City 0.
  Second Half ends, Manchester United 2, Leicester City 0.
  Kasper Schmeichel (Leicester City) is shown the yellow card.
  Corner,  Manchester United. Conceded by Wes Morgan.
  Attempt blocked. Romelu Lukaku (Manchester United) right footed shot from the right side of the box is blocked. Assisted by Marcus Rashford.
  Corner,  Leicester City. Conceded by David de Gea.
  Attempt saved. Islam Slimani (Leicester City) right footed shot from the left side of the six yard box is saved in the bottom left corner. Assisted by Demarai Gray with a cross.
  Foul by Marcus Rashford (Manchester United).
  Danny Simpson (Leicester City) wins a free kick in the defensive half.
  Offside, Leicester City. Wes Morgan tries a through ball, but Demarai Gray is caught offside.
  Corner,  Leicester City. Conceded by Antonio Valencia.
  Matty James (Leicester City) is shown the yellow card for a bad foul.
  Marcus Rashford (Manchester United) wins a free kick in the attacking half.
  Foul by Matty James (Leicester City).
  Corner,  Manchester United. Conceded by Wilfred Ndidi.
  Attempt missed. Islam Slimani (Leicester City) header from the centre of the box misses to the right. Assisted by Demarai Gray with a cross following a corner.
  Corner,  Leicester City. Conceded by Nemanja Matic.
  Video Review:.
  Goal!  Manchester United 2, Leicester City 0. Marouane Fellaini (Manchester United) right footed shot from very close range to the centre of the goal. Assisted by Jesse Lingard.
  Attempt blocked. Jesse Lingard (Manchester United) right footed shot from the left side of the box is blocked. Assisted by Marcus Rashford.
  Attempt missed. Demarai Gray (Leicester City) right footed shot from outside the box misses to the right. Assisted by Islam Slimani.
  Foul by Daley Blind (Manchester United).
  Riyad Mahrez (Leicester City) wins a free kick on the right wing.
  Substitution, Leicester City. Islam Slimani replaces Jamie Vardy.
  Substitution, Manchester United. Jesse Lingard replaces Anthony Martial.
  Attempt missed. Romelu Lukaku (Manchester United) left footed shot from outside the box is too high. Assisted by Marouane Fellaini with a headed pass.
  Substitution, Manchester United. Marouane Fellaini replaces Henrikh Mkhitaryan.
  Attempt saved. Demarai Gray (Leicester City) right footed shot from outside the box is saved in the bottom right corner. Assisted by Christian Fuchs.
  Attempt saved. Romelu Lukaku (Manchester United) left footed shot from the left side of the box is saved in the bottom left corner. Assisted by Paul Pogba.
  Goal!  Manchester United 1, Leicester City 0. Marcus Rashford (Manchester United) right footed shot from the centre of the box to the high centre of the goal. Assisted by Henrikh Mkhitaryan with a cross following a corner.
  Corner,  Manchester United. Conceded by Harry Maguire.
  Substitution, Manchester United. Marcus Rashford replaces Juan Mata.
  Attempt missed. Riyad Mahrez (Leicester City) right footed shot from a difficult angle on the right misses to the left. Assisted by Andy King.
  Attempt missed. Wilfred Ndidi (Leicester City) left footed shot from outside the box misses to the left.
  Attempt blocked. Riyad Mahrez (Leicester City) left footed shot from the right side of the box is blocked. Assisted by Demarai Gray.
  Corner,  Manchester United. Conceded by Danny Simpson.
  Foul by Romelu Lukaku (Manchester United).
  Wilfred Ndidi (Leicester City) wins a free kick in the defensive half.
  Substitution, Leicester City. Andy King replaces Shinji Okazaki.
  Substitution, Leicester City. Demarai Gray replaces Marc Albrighton.
target: Substitutes Marcus Rashford and Marouane Fellaini both scored as Manchester United overcame a resolute Leicester to strengthen their position at the top of the Premier League.