1. Fellaini enjoys villainous role, as both bosses tweak
Louis van Gaal opted for a 4-3-3 formation, with Jesse Lingard and Marouane Fellaini the furthest forward of the midfield three and Michael Carrick at the base of the trio. Juan Mata was out on the right-hand side and Anthony Martial on the left wing, with Marcus Rashford through the middle as the lone striker.
With Liverpool in a 4-2-3-1 shape, it meant that Jordan Henderson and Emre Can were able to sit in front of the defence and track the runs of Manchester United's midfielders. Henderson is naturally full of energy but even he struggled with the directness and inventiveness of Lingard in the opening 45 minutes. If Van Gaal can take one positive from this match, then it's the young Englishman's display.
Can was able to resume his ongoing feud with big-haired enforcer Fellaini, as the former Everton hero played up to his role of pantomime villain to the 3,000 travelling fans from across the M62. The German rarely beat his contemporary in the air, but his sheer presence made it difficult as they enjoyed an intense physical battle.
Jurgen Klopp kept a similar line-up to the first leg, with James Milner replacing the injured Alberto Moreno at left-back the only difference. Milner's endeavour and work rate ensured he didn't look out of place, and he caused a threat in an attacking sense with his crossing ability.
2. Manchester United show some initial intent
The biggest criticism of Manchester United this season at Old Trafford has been that, for all their possession, they've lacked penetration and tempo. They certainly provided a sense of urgency in the first half, although initially struggled to create any clear-cut chances. It took until the 19th minute before Simon Mignolet was called into action, when Marcos Rojo's cross was met by the head of Lingard.
United then started to increase the pressure on Liverpool, as Mata shot wide from the resulting corner. Both Martial and Rashford began to run in behind the away team's defence and looked to commit their opponents. Two minutes later Martial beat two defenders before his shot was blazed over the bar.
Nathaniel Clyne appeared a little less assured than in the first meeting at Anfield and he conceded a penalty on this occasion, having won one last time around. Martial converted the spot-kick, after his coming-together in the area with the Liverpool right-back.
For 15 minutes, United were in the tie and they had their arch rivals bordering on concerned. But as half-time approached, a moment of brilliance effectively ended the Red Devils' hopes. Philippe Coutinho superbly rounded Guillermo Valera and then expertly chipped the on-rushing David de Gea. The young Uruguayan right-back never returned in the second period, as Antonio Valencia came on.
"We played like Liverpool did in the home match with us," suggested Van Gaal. "We created a lot of chances in the first half and scored a penalty."
3. Sakho-Lovren partnership is growing stronger
The two centre-backs have had some horrific moments in their Liverpool careers, but are beginning to show their true value in tandem. Both players are strong in terms of distribution, strength and tenacity, although neither looks entirely comfortable for a whole 90 minutes.
Dejan Lovren looked to play a number of direct passes into the forwards, as Klopp's men bypassed the midfield at times. At one point his interception and anticipation lead to him providing a cross in attack, when he raced upfield with the ball. The former Southampton defender has maintained his confidence throughout his ordeal and seems a different player under the German coach.
Mamadou Sakho was also outstanding and heard his name chanted regularly by the away support. He was arguably Liverpool's best player on the night and never shirked his responsibilities. The Frenchman is unorthodox in his mannerisms, which invites the negative judgement on his attributes, but appearances can be deceptive and anyone studying his overall game will surely have been impressed.
"Sakho and Lovren were not too bad to be honest," Klopp admitted somewhat back-handedly after the match. "They had to find legal solutions which is sometimes not so easy."
United had their opportunities in the second half, but Liverpool never looked uncomfortable. Without a recognised striker on the bench, Van Gaal had few options as they chased the game and the Dutchman's changes did little to impact the outcome.
4. Origi makes case to start ahead of Sturridge
With the exception of Moreno this is Klopp's strongest XI, although Daniel Sturridge still doesn't look fully up to speed and appears a little laboured in comparison to his very high standards.
Just after United took the lead, the England striker did spring into life as he was upended by Daley Blind on the edge of United's penalty area. Sturridge's free-kick struck the crossbar, but it was the only time that the forward looked like scoring despite finding himself in good situations throughout the encounter.
The former Manchester City and Chelsea attacker didn't seem quite right, and would perhaps benefit from a couple of matches' rest. Divock Origi has been the perfect substitute for Sturridge around the hour mark in recent weeks because he shares a number of characteristics with his more senior team-mate.
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However, right now the Belgian has a little more energy in his forward movements. Straight from his arrival he showed why Blind is susceptible to pace, as he twisted the Dutchman one way and then another. His introduction made United a little more conservative than you might expect of a side chasing a three-goal margin.
With seconds remaining of normal time, Origi combined with fellow substitute Christian Benteke, only to hit his effort straight at De Gea. United didn't offer enough over the distance of the two legs, as Liverpool progressed to the quarter-finals.
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