A deleted scene from Thor: Ragnarok, but Hulk's screentime in Infinity War proved to be minimal.
Hulk is one of the first characters featured in Infinity War, as he surprise-attacked Thanos in the beginning. This proved to be the only scene where Hulk was out in full-force, leaving Banner on the sidelines of some battles before eventually putting on the Hulkbuster armor in the end. It wasn't until Avengers: Endgame that Hulk re-appeared, and this time it was as Smart Hulk. Bruce found a way for himself and Hulk to coexist during the five-year time jump, but the original plan for Smart Hulk would've seen this transformation happen in Infinity War.
The original plan for Smart Hulk's MCU arc saw him emerge during the third act of Infinity War. It was supposed to happen when Bruce Banner, in the Hulkbuster armor, was near defeat at the hands of Cull Obsidian. In the final version of the film, Banner manages to defeat Obsidian himself after Hulk refuses to emerge. The fallout of this transformation was then set to see Smart Hulk encounter Black Widow and Falcon shortly after, with Natasha attempting to calm Hulk down as she did in Avengers: Age of Ultron - only to discover that he no longer needed calming down.
The decision to change Smart Hulk's role in Infinity War and delay the transformation until Endgame came during production, as Bruce's role in Infinity War was reshot. The late-change is why some of the CGI with Bruce (and his floating head) in the Hulkbuster suit are so apparent near the end. This plan also highlights how Infinity War's big team-up shot throughout the marketing wasn't supposed to be completely misleading. While that specific shot wasn't going to be in the movie, Hulk's inclusion makes sense since he was going to be there originally.
The writers of Infinity War have attributed the the transformation happening off-screen. What Avengers: Infinity War ultimately did with Hulk still works, but the deleted scenes (which can be seen on the Infinity Saga box set) point to the original plan being superior.
