The 28-year-old marked his seventh league appearance of the season with a goal in United's 4-1 win over Newcastle United last weekend as the second-placed side maintained their eight-point gap behind leaders Manchester City.
"I don't feel like I really need to prove anything to Gareth because I play under one of the biggest and most successful managers in Jose (Mourinho) and he's only going to pick the best players," Smalling told reporters on Tuesday.
"...I think ultimately if my season carries on like this and we have a successful season and our team still concedes very few goals, then I think it gives him maybe no choice in the summer but to pick me (for the 2018 World Cup).
"I've been getting a good run of games over these last few months and I'm feeling good and that's the feeling you want, you want to be able to play regular games and be a part of a successful team."
Smalling is confident of earning a spot in England's World Cup squad provided he plays regularly for United and backed the side to surpass last season's haul when they won the League Cup and Europa League.
"I think, ultimately, it is your club form that decides whether you play at a World Cup because there aren't that many England games throughout the season," Smalling added.
"While I'm playing regularly here and being a part of a very successful team I think that should show come the summer."
United, who need one point to progress to the Champions League knockout stages, host Brighton and Hove Albion in the league on Saturday.
(Reporting by Aditi Prakash in Bengaluru)
