The defender, who joined United officially in the summer, was one of ten players brought into the starting line-up by Sir Alex Ferguson as the Reds kicked-off their European campaign at Old Trafford.
Smalling impressed alongside skipper Rio Ferdinand and, despite the disappointment of dropping two points, enjoyed every minute of his run-out.
"It's one of the biggest competitions a player can play in and I thoroughly enjoyed it," he told MUTV.
"I've watched so many of these games on television so to be part of one at a club like United is fantastic.
"Unfortunately, we just couldn't break them down and everyone is disappointed with the result.
"The next game against Valencia [on 29 September] is going to be very important now. Hopefully we can move on quickly from this result, take the positives from it and score a few more goals in our next few games."