We're just over three weeks away from the Royal Rumble, and WWE continued the build towards the event this week on Monday Night Raw and SmackDown Live by adding more matches to the show as well as more participants to the Royal Rumble match.In the main event of SmackDown this week, Daniel Bryan added a WWE Championship match to the Royal Rumble, forcing AJ Styles to defend his title at the event in a 2-on-1 handicap match against Kevin Owens and Sami Zayn.As well as this match, the other matches booked for the Royal Rumble pay-per-view so far include the men's and women's Royal Rumbles, the final of the United States Championship tournament, and the triple threat between Brock Lesnar, Kane, and Braun Strowman for the Universal title.The match card for the Royal Rumble is almost full, and the spots in the Royal Rumble matches are filling up quickly too, and it is this booking that could possibly stop four big SmackDown superstars from competing in the Royal Rumble match.Reports have stated that Bobby Roode is expected to face Jinder Mahal in the final of the United States Championship tournament at the Royal Rumble, and The Glorious One is likely to walk out as the new United States Champion.According to WrestleVotes, if Roode does advance to the final of the tournament at the Rumble, he may not be in the actual Royal Rumble match later on in the evening. WrestleVotes also stated the three competitors involved in the WWE title match, Owens, Zayn, and Styles, will also not be in the Royal Rumble match.

This leaves SmackDown very light on star power in the Rumble compared to Raw, as the only big superstars in the match are Randy Orton, Shinsuke Nakamura, and Baron Corbin, with The New Day as well although they are yet to confirm they will be participating in the match.

It will be a shame if Roode, Owens, Styles, and Zayn miss the Rumble match, as we have seen superstars compete in two matches at the Royal Rumble before. Roman Reigns did it last year after he battled against Owens for the Universal title and then competed in the Rumble later on in the show, so it's not entirely impossible.

In 2016, several superstars competed in singles matches as well as the Rumble match, so just because a superstar competes earlier in the night, doesn't mean they'll not be in the Rumble match.