United scored all of its goals after the break to earn a 3-0 win over Colchester, which arrived at Old Trafford in ninth place in the fourth tier and defended stoutly before Marcus Rashford's opener on the counterattack in the 51st minute.
The neighbors were then paired in the draw for the two-legged semifinals, for a repeat of their last-four meeting in 2010 that saw United advance thanks to Wayne Rooney's injury-time goal in the second leg at Old Trafford.
Leicester, which is in second place in the Premier League, will start as favorite in the other semifinal against Aston Villa after beating Everton 4-2 in a penalty shootout, having squandering a two-goal lead to draw 2-2 after 90 minutes.
Villa thrashed a heavily weakened Liverpool team 5-0 on Tuesday. The first legs of the semifinals take place on Jan. 7 and 8. The returns legs are two weeks later. STERLING DOUBLE Sterling started in the unusual position of lone striker and provided more evidence of the improvement in his finishing, which has largely been credited to the coaching under City's assistant manager Mikel Arteta.
Seemingly on the verge of taking charge at former club Arsenal, Arteta was in the dugout for City for perhaps the final time and saw Sterling show good movement to score within five minutes of a surprising equalizer by Oxford just 21 seconds after halftime.
Sterling added a third goal in the 70th minute, again from close range from a central position. “I am there to put them in, no matter how they come,” Sterling said. City, which took the lead through right back Joao Cancelo's first goal for the club in the 22nd, allowed 18 shots - 16 coming in the second half - to a team that is in eighth place in League One. According to stats supplier Opta, that's the most shots City has faced in a single match under Pep Guardiola in his 3 1/2 years in charge.
“I am really pleased with the players,” Oxford manager Karl Robinson said, “but my last thought tonight will be, ‘What could have been.’” UNITED TOILS Colchester, the lowest-ranked team in the quarterfinals, held its own against United until breaking clear early in the second half and having its best sight on goal.
Within 15 seconds, United had counterattacked - starting with a quick throw-out by goalkeeper Sergio Romero - and Rashford cut inside from the left before firing a rising shot into the net. An own-goal and a close-range finish by Anthony Martial sealed an ultimately comfortable win, and a meeting with a cross-town rival which it beat in the league this month.
LEICESTER KEEP ROLLING An unlikely title challenger in the league, Leicester has another shot at a trophy after Jamie Vardy converted the winning penalty in the shootout at Goodison Park to send his team into the League Cup semis for the first time since 2000 — the year it won the competition.
Leicester goalkeeper Kasper Schmeichel had earlier saved spot kicks from Cenk Tosun and Leighton Baines in the shootout. Goals from James Maddison and Jonny Evans in a three-minute span put Leicester 2-0 ahead after 29 minutes, only for Everton to come roaring back through strikes by Tom Davies and then Baines in injury time.
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Steve Douglas is at www.twitter.com/sdouglas80