A Zlatan Ibrahimovic-inspired United came out on top at Wembley as they beat their Premier League rivals 3-2, with the Swede heading home late on in a game that had appeared to be going to extra time.
And the triumph was a significant one in that it nudged the Red Devils ahead of their great north-west rivals in terms of total silverware won - United now being on a total of 42 compared to Liverpool's 41.
And Smalling took the chance to point out the tally in a dig on social media, tweeting "WATCH THE THRONE" in an apparent reference to the two club's trophy hauls.
Supporters of the Anfield club were clearly not impressed with Smalling's antics, however, biting back at the England defender in a series of replies to the 27-year-old.
Following the League Cup win, United now turn their attentions back to league matters, with Mourinho's side facing Bournemouth on March 4 before a trip to FC Rostov in the Europa League.