Jesse Lingard added the Red Devils' second goal on a cross by Tyler Blackett in the 65th, just two minutes after coach Louis van Gaal subbed out his entire starting 11 to play the second team yesterday.
Adnan Januzaj scored for Man United in the 90th minute, some 30 seconds after Rafinha got Barcelona on the board in the 90th.
The Red Devils improved to 3-0 in the International Champions Cup, this time getting the best of Luis Suarez and Barca while playing under clear skies for a sellout crowd of 68,416 at the USD 1.3 billion home of the San Francisco 49ers.
Van Gaal subbed his entire team in the 63rd minute as planned. Now, his team will wrap up its preseason tour against Paris Saint-Germain on Wednesday at Chicago's Soldier Field. UEFA Champions League winner Barcelona will look back on its missed chances.
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Luis Suarez hit long shots off each post, and Ivan Rakitic's ball just skimmed the top of the net in the 59th. Suarez had a goal negated for being offside in the 61st, though it appeared he was fouled in the box by Daley Blind moments earlier.
Barca beat the Los Angeles Galaxy 2-1 on Tuesday night in front a record 93,226 at the Rose Bowl in the team's first game of its preseason tour in the U.S. Barcelona will face Premier League champion Chelsea on Tuesday at FedEx Field in Landover, Maryland.
The La Liga champion is playing without Lionel Messi and Neymar as both are skipping the three-game tour to be fresh for games that count.