The 27-year-old was choosing players he has played with at Old Trafford, having joined United in 2010 and played under four managers in that time.
Speaking to ManUtd.com, he explained his decision to include Valencia over Rafael da Silva or Gary Neville, the latter of whom played very little with Smalling due to injuries.
“Right-backs have changed a lot but I’m going to go with Antonio,” Smalling said.
“When I first joined he was a right midfielder but he has made that right-back position his own over the last few years and I don’t feel there’s any player who’s going to beat him in a one vs one duel.”
Smalling didn’t choose himself or any of his defensive partners, instead going for Rio Ferdinand and Nemanja Vidic, one of the Premier League’s best ever centre-back pairings.
“When I signed both were in their prime,” Smalling explained. “And I got to train with them and play with both and learn a lot from them.”
Smalling’s dream Man United XI in full: David de Gea, Antonio Valencia, Rio Ferdinand, Nemanja Vidic, Patrice Evra; Paul Scholes, Michael Carrick, Ryan Giggs, Paul Pogba; Wayne Rooney, Marcus Rashford.
Quite how a midfield four of Scholes, Carrick, Giggs and Pogba would work will never be seen, but though Smalling has played for United during one of the club’s lesser periods, he has picked a fearsome line-up with incredible talent.
It is also evidence of the ability of the current United side that four of the players can enter a dream XI of Smalling’s given the Englishman was part of the squad that reached the 2011 UEFA Champions League final under Sir Alex Ferguson.