Despite a No. 1 finish at the box office, execs at Warner Brothers have to be concerned.

The LEGO Batman Movie may have won the weekend with $55.6 million over Fifty Shades Darker ($46.7 million) and John Wick: Chapter Two ($30 million), but that number could signal weakness in two of the studio's franchise pillars.

Here are four reasons WB studio execs may be restless:

1)  The LEGO Batman Movie fell well short of industry expectations, which pegged the film as having a $76 million opening weekend. That $20 million difference is significant and will translate to the film falling well short of The LEGO Movie, which opened on the same weekend three years ago and debuted with $69 million and finished with $257.7 million domestically. In contrast, The LEGO Batman Movie will likely have to fight to squeak past $200 million. Which should worry Warner Brothers, because...

2) If filmgoers are already losing interest in the Lego franchise, that's trouble. After the critical and commercial success of The LEGO Movie in 2014, Warner Brothers slated three LEGO films as part of their "three blockbuster franchise pillars" to compete with the blockbusters from Disney (Star Wars, Marvel Studios, Pixar, Disney Animation and Disney Live-Action) and others. Warners was also finally planning a DC Movie Universe with 10 films and 3 more adventures in the "Potter-verse" with at least 3 (now 5) films written by JK Rowling – although Fantastic Beasts vastly underperformed the actual Harry Potter films. But if the immediate follow-up to The LEGO Movie with the added attraction of Batman and his allies and rogues is showing declining interest, that does not bode well for Ninjago, set to open on Sept. 22, or The LEGO Movie 2, set to open on Feb. 8, 2019. Even more concerning...

3) If filmgoers are starting to tire of Batman, that's BIG trouble. Ever since Superman II in 1981, DC/Warner Bros. has had a very hard time getting any other superhero property to the big screen - and when they do, they are almost always critical or commercial disappointments. The one exception has been Batman. Batman is the closest thing DC Entertainment has to a sure thing - so much so, that when Man of Steel finished it's box-office run below expectations, they immediately trashed plans for Man of Steel 2 and went about making Batman v. Superman: Dawn of Justice - and they began the Batman villain franchise, Suicide Squad. While the $330 million domestic take for Batman v. Superman is hardly chicken feed, it is disappointing when you consider DC/Warners was hoping this historic clash, plus Wonder Woman, would do close to Avengers or Dark Knight numbers (over $600 million adjusted). Batman v. Superman ended up making less, adjusted for inflation, than all but two of the eight live-action Batman films to date - and those two were the films that almost sank the Bat-franchise (Batman and Robin) and the film that underperformed due to that film's still bitter taste (Batman Begins).

4) If The LEGO Batman Movie continues to underperform, it will put more pressure on Gal Gadot and Wonder Woman to show a non-Bat DC film can do massive numbers. Either way, it is not the sort of momentum DC/Warner Brothers surely wants with The Batman solo movie, Justice League, Gotham City Sirens and so many other Bat-relayed films making up their schedule.