The Challenge: USA is heating up, as the players compete for the grand prize of $500,000. With almost half of the cast eliminated, the competition is getting fiercer. Host TJ Lavin’s algorithm twist, which was revealed after the first challenge, made it impossible for team members to know who they will be paired up with for the next daily challenge.

This week, Big Brother alum Derek Xiao was teamed up with Love Island USA star, Shannon St. Clair. The daily challenge had the competitors climb up a big rig, memorize numbers, jump into the water, and then solve an equation. Unfortunately, Shannon pulled a hamstring during her run, and this left her at a disadvantage.

Related: Why Big Brother's Xavier Prather Was Hesitant To Go On The Challenge USA

Despite trying to pass off her injury as nothing major, the daily challenge winners, Desi Williams and David Alexander, found Shannon to be a weak link, and found it easy to decide to throw her and Derek into the elimination. The two competitors had to face off against Enzo Palumbo and Justine Ndiba, and although it was a close race, Derek and Desi’s strategy didn’t stack up.

Screen Rant: This was a complicated challenge. I had trouble keeping up as TJ was explaining the rules. How are you able to remember all the steps?

Derek: There were four colors, and it was like red, blue, yellow, green, let’s say. So RBYG. So then me and Shannon were just using RBYG and memorizing a number. So if it was one red, it would be 1000, and then if it was a green, it would be a 1001. The entire time we were just trying to memorize one number. At the end, the final number was like, 2,432, so it was 2 red, 4 green, 3 red, whatever. I felt like that was a good idea, but it ended up being kind of hard because we misremembered. It was good in theory, it was wrong in practice.

Both of you were not in physical shows before The Challenge. How did you prepare for it going in?

Derek: Minimally.

Shannon: I was supposed to be an alternate. I wasn’t supposed to be on The Challenge, so I didn’t train, I didn’t watch the show. I kind of felt like I was very vulnerable in my position, getting thrown in and not practicing, because I have a very much a winner’s mindset. Like, I don’t lose. So I just felt so unprepared that I didn’t do my homework. I didn’t watch Survivor. I didn’t even know the other shows, so I did not train at all for The Challenge. If I knew I was going on, I would have done everything opposite. I would have prepared and have done everything differently.

Derek: You know it’s unfortunate because I knew I was going to go on the show and I still didn’t train. So, I wish I had Shannon’s excuse, but I tried to train for about the month leading up to the show. I’m in regularly pretty decent shape, but I was like I gotta up it to the next tier, so I contacted the best personal trainer I knew, Kyland Young. I was like, "Yo, can you whip me into shape?" He had already been training for The Challenge, so I just hopped into his workouts. But he trains different. So we would run this two-mile hill together and the very first time that I did it, I said, "Yo, Kyland I don’t think I could do this," and he talked me into it. I started walking to the hill, and he puts on another 45 lb vest and does the hill with me. And then, we get to the top of the hill, and he gives me a 20-digit number to remember. I have 30 seconds to remember the number, and we would run back down to the bottom of the hill, and he quizzes me on what the number was. Every digit that I got wrong, I had to do like a burpee or whatever. This guy is insane. It is in his future to win The Challenge.

How did you feel when Desi and David were deliberating and Desi said you guys were an “easy throw in?”

Shannon: I feel like from my perspective on it, I was injured. I also didn’t have an alliance with Desi and neither did Derek so speaking for myself, I didn’t talk to Desi so much. We had a good personal relationship after the show, and we were really nice to each other inside the compound, but we never talked game together, which was our first mistake. And then me having an injury I knew that the people weren't going to want to get to a final with me if I was injured. So I did see it coming. I did know that there were other pairs that could have gone in.

Derek: I mean straight up, Desi might be able to bench more than me, so I’m not even offended by that. Physically for sure, I was not there with the other guys. My entire pitch, I was like, I hadn’t won any challenges, so I was saying things like, “My friends will mess you up if you throw me in. You see the people back there? I got Kyland, I got Angela. They’ll mess you up! You don’t want this smoke.” She was like, “Are you going to give me smoke?” I was like, “Not me but like…hold me back, hold me back.”

When they did say your names in the arena, were you blindsided, or did you know you had a target on your backs?

Shannon: I didn’t feel like we were blindsided because David and Desi actually pulled us aside privately right before and told us that they were not blindsiding us, and they were going about it in a decent way to let us know right before we went in so our respect to Desi and David. No hard feelings there whatsoever. I felt like that was the first time anyone’s done that.

Derek: For sure, I think it was definitely a stand-up move to do. I feel like the target shifted so much that day and having to talk to Desi outside the game. We were always Desi’s number one pick. For her, it was always going to be us and I kind of had the sense that was the case, so I was trying to pitch David the entire day. I didn’t talk to Desi until like, 6 pm that day and elimination was at like, 7. So I was pitching David the entire time, and I was really hoping he would swing Desi, but it’s tough because you and your partner have to come to a unified decision. From their perspective, I saw it. I saw the reasoning why and it definitely made sense.

What did you think of TJ’s twist in the elimination with the Spelling Bee? Derek, you seemed excited about that.

Derek: I was honestly way too excited. My inner nerd came out. I heard spelling bee and I was like, "Let’s go!" I thought the entire elimination was going to be spelling. I was so excited. I was like, I’m not even going to have to run, I have to stand here and spell words, and then we would go home. But watching it back, I was like, I look so lame right now cheering that hard for a spelling bee.

Shannon: I mean, it was nerve wracking. For example, Justine got "cynical" and I got "goggles." I’ve been getting a little heat on Twitter. I didn’t pick the words, but for me, I wouldn’t put the two in a category at all. I think my girl Justine got robbed on that word, but they ended up winning so…

That was one of the closest eliminations. Even TJ lost his voice screaming for you guys. Where do you think your stacking strategy went wrong?

Derek: Pretty clearly, we all saw where it went wrong. 100% those tires were like the Leaning Tower of Pisa. My original idea was to overcompensate for a height disadvantage because we couldn’t reach some of the tops of the tires, so I was thinking because I’m a little taller I was going to stack up and then Shannon could stack around so you don’t have to lift the tires as high, you don’t have to use more muscle groups. I thought that was going to be a good plan. But these tires ended up being deflated so as soon as you stack a tire on, it didn’t have any rigidity, and they would just fall off and that ended up being what lost us the challenge - not stacking them properly with a strong foundation.

Shannon: Just for reference, I am 5’1 and Derek is 6 feet and even in the beginning of the elimination the poles were around 10 ft or so and Derek had to step on his tippy-toes to get them off so that was another issue that we ran into. A little behind the scenes that wasn’t shown was Derek had to make a stepladder for me with two tires so that I could climb up and get them off. I felt like the height disadvantage was really frustrating for me.

Shannon, on a scale of one to ten, how bad was your hamstring?

Shannon: Also a little behind the scenes, it was a ten for sure, because I hurt it the first time in the daily and what wasn’t shown was we actually got the equation a couple of numbers off. I had to go run and jump and do it all over again with the pulled hamstring. So I was climbing up the ladder with one leg out. I was screaming, it was really bad. It looked like I only went once and then got to rest all day. We had to go back and do it again, which meant it tore even more the second time around. I went to medic, I numbed it with a numbing spray in the ambulance right before the elimination, I was taking medication, tiger balm, wrapping it, you name it. It was really, really bad. It actually wasn’t the first injury. I tore it prior doing cheerleading.I was on a travel team, so it was like PTSD for me. But I can’t limp around the compound. I can’t lay in bed all day. I can’t show that I’m really hurting because we already had a big target on our back, so I was running. My leg was numbing as I started to run which helped a little bit. In the sand, it was really, really bad. It hurt a month after I left the Challenge. It was the worst pain ever. It was so frustrating.