United travel to Sunderland in the league on March 30, before facing Chelsea for a place in the FA Cup semi-finals just two days later, and Smalling believes that they will be an important few days.
"When we come back it's two games in three days and that could be a key few days for us in terms of both the Premier League and FA Cup. They will be big games for us," Smalling told The Sun. "We can't rest on our laurels and we have to make sure we finish it (the title) well before the season is over.
"The manager said that at this time of year there can be a lot of 1-0 wins which can be ugly, but you just need to get the three points.
"So it's just a case of moving on from this. It wasn't great but we need to come back from the internationals ready for some big games."
Smalling has been named in the England squad for their World Cup qualifiers against San Marino and Montenegro.