When Martin Henderson joined the cast of Grey's Anatomy shortly after the onscreen death of Derek Shepherd (Patrick Dempsey), he knew he had big shoes to fill. But it's possible he didn't realize how big.

Now that Henderson's character, Nathan Riggs, and Derek's widow Meredith (Ellen Pompeo) have dabbled in romance and seem to be heading towards a full-blown relationship, Henderson is, predictably, facing some comparisons to the character fans knew as Dr. McDreamy — and not all of them are favorable.

"I think it's inevitable, if you bring in a new character, there's going to be resistance and negative emotions as well as positive," Henderson told TVGuide.com at a Grey's Anatomy PaleyFest event earlier this week. "For me, it's just fun to sort of be a part of that and see the audience grapple with it. Because I think even the people that sort of go, 'Oh, I hate Riggs,' it's a testament to how much they love the show and obviously how much they love Derek."

Grey's Anatomy: Justin Chambers weighs in on the Jo or Meredith debate

Though it seems like Grey's fans are resistant (to put it mildly) to move beyond MerDer, Henderson isn't taking the criticisms personally.

"It's so out of my control," he says. "I can't determine how they write the character. I can't determine how they write the relationship."

Check out the video to see what else Henderson has to say about the McDreamy comparisons.

Grey's Anatomy airs Thursdays at 9/8c on ABC.