Alejandro Garnacho's late finish was cancelled out by an even later effort from City's Bernardo Silva, forcing penalties, which the Reds narrowly lost.
Despite this, United looked threatening throughout, with the performances of Garnacho and Amad in particular standing out ahead of the start of the Premier League season on Friday - against Fulham at Old Trafford.
Speaking to MUTV and other media outlets following the disappointing defeat in the capital, Erik was keen to remain positive, reiterating the importance of using the loss as fuel for the new campaign.
USE PAIN AS MOTIVATION
"You have to feel the pain.