The Last of Us draws a lot from Naughty Dog's Uncharted series. Both are third-person cover shooters utilizing the same engine. And for a while, it did seem like The Last of Us would be merely "Uncharted in hardcore mode." (Thankfully, the end result was much more inspired.)
Neil Druckmann, lead designer of Uncharted 2 and creative director of The Last of Us, talked about how a cut idea from the Uncharted games led to the genesis of their survival horror world.
"When Bruce [Straley, game director] and I were working on Uncharted 2, we would brainstorm a lot of gameplay scenarios or story scenarios," Druckmann told VentureBeat, describing a scenario he called The Mute Girl. "We started to brainstorm how you would form a bond through gameplay, where you can't rely on dialogue. She would shake Drake awake in the middle of the night and motion for him to follow her... As you're climbing up on this rooftop of this building, you get to see a vista over this whole city as it's lit up. You hear gunfire and stuff in the distance, but it's this really beautiful moment that you get to share with this character, all through gameplay."
Although that scenario didn't make it into the Uncharted games, it led to the question that propelled the development of TLOU: "could you build an entire game around this concept of meeting a character really early on and forming a bond that would evolve and shift as you see all the facets that a deep relationship between two people can have?"