We already know that Alex Karev (Justin Chambers) is in seriously hot water when Grey's Anatomy returns for Season 13 this Thursday. But any legal repercussions he might face for beating up Andrew DeLuca (Giacomo Gianniotti) may pale in comparison to the blowback he's going to receive from his colleagues at Grey Sloan, not to mention his girlfriend Jo (Camilla Luddington). In fact, the incident divides pretty much the entire staff at Grey Sloan, and may cause irreparable damage to some longstanding friendships and relationships as a result.

"The last thing that we saw was Alex beating the crap out of DeLuca. That has some serious repercussions ... in the relationship between the doctors in the hospital, having to reckon with the notion that one of their own could have been so violent," Grey's star Kelly McCreary tells TVGuide.com. "There's a pretty intense fallout from that impulsive behavior from Karev. ... It causes some friction among the doctors. There's definitely sides being taken."

McCreary previously teased that Season 13 will focus on "the originals" - i.e. the few remaining characters who have been a part of the show since Season 1: Meredith (Ellen Pompeo), Karev, Bailey (Chandra Wilson) and Richard Webber (James Pickens Jr.). For Meredith and Karev, Season 13 will mark a turning point in their relationship as Meredith's immediate impulse is to empathize with and protect her BFF.

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"You would think that you would take the side of somebody who's been beaten up, but these doctors have long histories together, and so I think it's just human nature to want to make sure you have all the information before you take sides," McCreary says. But inevitably, if you have a long history with somebody, that informs any new information you get about them."

And all of that doesn't even touch on what's maybe the biggest question: Will Jo and Alex be able to move forward after her revelation that she's married to someone else? It's obvious that Alex is already struggling with major trust issues after Jo dropped her bombshell, targeting DeLuca because he believed he and Jo were hooking up.

Unfortunately, we may have to wait to get an answer to that question and more. The season premiere - which picks up about 10 minutes after the Season 12 finale - is so focused on the immediate fallout from Karev's assault on DeLuca, many of the other dangling threads from last season won't get picked up until Episode 2 at the earliest.

Grey's Anatomy Season 13 will focus on "the originals"

"Because DeLuca's badly injured, there's an immediate medical emergency. Taking care of him sort of takes center stage," McCreary cautions.

Just how badly injured is DeLuca? Only time will tell. And among the other storylines that need to be dealt with are Callie (Sara Ramirez) leaving the show, April (Sarah Drew) and Jackson (Jesse Williams) trying to figure out how to be parents, Owen (Kevin McKidd) and Amelia (Caterina Scorsone) navigating married life, and Maggie's (McCreary) revelation to Meredith at the end of Season 12 that she has the hots for Riggs (Martin Henderson).

"Maggie clearly is in a moment of great hope and optimism, and she remains in that place for a while ... while Meredith figures out how to manage this new information," McCreary says. "Meredith is still totally processing all of this. For the moment, it's like Maggie has sort of put Meredith between a rock and a hard place. ... She's going to face a major disappointment at some point. But it does not reveal itself in that first episode."

Grey's Anatomy kicks off Season 13 Thursday at 8/7c on ABC.