The alarming incident takes place on a difficult day at work for Sacha, who is fighting to convince new medic Ella not to quit.
Just as Sacha seems to be making progress with Ella, events take a sudden twist as two patients become violent with each other. When one grabs a scalpel, it's Sacha who's left seriously injured as he tries to break them up - and a panicking Ella leaves him for dead…
Digital Spy recently chatted to actor Bob Barrett, who plays Sacha, to hear all about the dramatic storyline.
Why does Sacha spend so much time supporting Ella?
"I think it's because he hates giving up on people. There's also a little bond between them - Sacha feels that Ella is misunderstood and a lot better than people think she is. He's on his soapbox and championing her slightly, so he feels he can help when everyone else is saying that she's useless and a waste of space!
"When Ella says that she wants to quit, Sacha persuades her to stay. Whenever people say that they don't want to be a doctor, Sacha will always insist, 'No, you do want to be a doctor - it's the best thing in the world!' He can't take no for an answer."
How does he feel about the responsibility of helping to train up a new recruit?
"It's not something that he takes on lightly. He thinks that once you hit the first couple of problems, you don't just give up on someone because of it. Sacha knows how much it takes to be a doctor - there's a lot of peaks and troughs involved. He's willing to fight people's corner more than most, and in that sense I think he's a good mentor."
How do things progress from there?
"Ella gets angry with Sacha on the ward, but he just smiles at her. She can't understand why he's smiling, so he takes her to the top of the hospital roof and says that he wants her to shout at the top of her voice! He promises that it will make her feel fantastic, and it does.
"Sacha then explains that this is what he saw on the ward - Ella has what you need to do the job, which is fire in your belly. He predicts that she's going to be a good doctor, and I think the viewers will agree with him at that point. But at the end of the episode, it all crashes to the ground as Ella rushes off after Sacha has been stabbed…"
How does the stabbing incident come about?
"The story surrounds two patients on the ward - a teacher called Colin Jenner and another character called Arlow, who's an ex-pupil of his. As they come face-to-face, they don't get along - and it all comes to a head when the teacher grabs a scalpel as they get into a fight.
"Sacha gets between them and it looks like he catches a blow to his stomach, but actually it's Arlow with the scalpel after grabbing it from Colin. So Sacha gets stabbed in the fight. It's one of those things that happens completely out of the blue."
How serious is Sacha's injury?
"Well, the scalpel hits an artery, and he bleeds out profusely. Chrissie manages to stop the bleed and Sacha then gets taken into theatre. Michael later reveals that Sacha is stable, but the next few hours are critical. It's incredibly serious and it's a life-threatening injury. I don't think the viewers will think that Sacha's going to die, but it's a terrible thing that's happened."
What was it like to film the storyline?
"I loved it - I got all excited when I heard that I was going to be stabbed! (Laughs) The filming day was such a great day. It took such a long time and we did it in such detail, so it was really great. I loved working with Emma Hiddleston who played Ella, as we got on so well. Everyone else on the ward that day was great as well - I really, really enjoyed it."
Will the storyline have long-term effects?
"I think there will be an aftermath and it's a long-term thing. Initially what happens affects Sacha quite a lot and I think once something like this has happened to a character, it's always there. He'll never forget it.
"But something like this can make a character stronger, too. It affects the relationship between Sacha and Chrissie as well, which is very interesting. If anything, it strengthens their relationship because of what they've experienced together."
Do you think Sacha and Chrissie are soulmates?
"I don't think they're soulmates, but I think they are fantastic for each other. Sacha truly loves Chrissie and, in her way, she loves him very, very much as well. I don't know where it's going to go, but I think it's a great and healthy relationship, as they see each other for who they really are and they're great parents to Daniel.
"Even though it's a very unlikely pairing, I think it's a very wholesome relationship and it's got a lot going for it. I don't think Sacha's ever met his soulmate, though."
After two years at Holby City, how are you finding your time on the show in general?
"I love it here and that's always been the case - since day one, I've had a ball. I love the cast, the crew and the people who run the show - it's a great team. I love being part of a programme that people hold dearly - and I feel the responsibility of that, too.
"It's great that people love the show and it's popular. In the past, I've done a lot of theatre seen by a handful of people, which is great. But it's also quite nice to do something that millions of people love."
How long would you like to stay on the show for?
"I think as long as you enjoy something, you should stay in it. Probably more importantly, as long as you think that your character has a journey, you should keep going with that. At the moment, it's hard to see a point where I wouldn't feel that - but there's bound to be at some point.
"I don't feel that I'm at the end of a story - I'm in the middle of a story, really. I think it's important to finish that. I don't want to leave it in the lurch, as people have been watching it for two years."
Has it been sad to say goodbye to Laila Rouass, Edward MacLiam and Olga Fedori recently?
"I didn't know Laila terribly well because we were on different wards, but she was fantastic - I loved her on screen and off. She was hilariously funny and great in the show, but I never had a scene with her! She was the only character in the show I didn't have a scene with.
"I loved Ed - he had the dressing room next to mine and we had great fun. But I'll miss Olga the most. I'll miss having scenes with Frieda, but Olga is a close friend so I'll miss her personally as well."
Are you enjoying working with Holby City's new arrivals?
"They're all great! I've known Catherine Russell, who's playing Serena Campbell, for ages. I did a play with her ten years ago, so I'm really pleased that she's come on board.
"Michael Thomson and Chizzy Akudolu have also joined the cast. I haven't actually worked with them as they're on Darwin, but luckily for me they're on my corridor and we get on like a house on fire. I think they'll be fantastic on the show - they're a breath of fresh air and a joy to have around."
> Read more 'Holby City' spoilers and news
Holby City airs Sacha's stabbing on Tuesday, May 15 at 8pm on BBC One.