Manchester United's Chris Smalling injured during warm-up against Liverpool

Chris Smalling battles for a ball. AFP PHOTO / Robyn BeckROBYN BECK/AFP/Getty Images

ANN ARBOR, Mich. -- Manchester United defender Chris Smalling was left out of the team that lost 4-1 to Liverpool after picking up an injury in the warm-up.

Smalling was listed in the team to face Liverpool at the Big House in Michigan on Saturday but did not emerge for kickoff.

He was replaced in the XI by Eric Bailly, who was not named in the squad at all when it was published by United an hour before the game.

The club described Smalling's unspecified problem as "minor" and his omission from the team as "precautionary."

It will, however, be another blow for manager Jose Mourinho, who already has seen first-choice right-back Antonio Valencia fly home from the United States with a calf injury.

Luke Shaw was also absent from the squad against Liverpool after being substituted during the game against AC Milan in Los Angeles on Wednesday.

With a number of senior players missing following the World Cup, Mourinho had been banking on Valencia, Shaw, Smalling and Bailly to start in defence against Leicester at Old Trafford on Aug. 10, the first game of the Premier League season.