KSI and the Sidemen have been ramping up their preparations ahead of their annual charity game on Saturday afternoon.
But there was one very unexpected figure present at Friday’s training session – NBA superstar Cooper Flagg.
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The Sidemen’s official X account posted a picture of the Dallas Mavericks’ No. 1 overall pick taking a selfie with the likes of Harry Lewis (Wroetoshaw) and Simon Minter (Miniminter).
Flagg, who is the leading frontrunner for the NBA’s Rookie of the Year award – albeit in a close battle with that of his former Duke Blue Devils teammate Kon Knueppel – revealed that he has been a huge fan of the Sidemen for a number of years.
Meeting Swedish streamer Marlon (Lundgren Garcia) on a live stream, Flagg could be heard saying in response to being asked whether he was a fan of Sidemen: “Yeah, growing up and stuff.”
Flagg also revealed that he was excited about being in attendance for the sell-out game which will be held at Wembley Stadium in London.
“I’m excited. It’s super cool. Wembley is 90,000 people – that’s a lot,” the 6-foot-8 forward said.
“I used to play [football/soccer] when I was younger, but not for a while.”
Fans stunned at the NBA-Football crossover
The interaction between the Sidemen and Flagg was a shocking one which left fans absolutely baffled on social media.
“What the **** is Coop doing there?” one user posted to X.
“This makes absolutely 0 sense, I’m just gonna assume Cooper was a fan growing up,” a second user commented.
“This is the most unexpected collab wtf,” a third added, while a fourth added. “I love that the new gen of athletes are just YouTube/gaming kids.”
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“Mystery player confirmed?” a fifth user questioned amid expectation of a surprise player competing in the match.
However, that is unlikely considering darts world no. 1 Luke Littler was blocked from participating despite his pleas due to KSI’s strict policy that it is for content creators only.
The Sidemen’s charity game has seen its popularity surge since its first iteration back in 2016, which was held at the 32,000-capacity St Mary’s Stadium – home to EFL Championship side Southampton.
In 2025, the match was streamed by more than eight million viewers on YouTube.
And tickets for this weekend’s match reportedly sold out in record time, KSI – who is now co-owner of EFL side Dagenham & Redbridge – exclusively revealed on eSPORTY Breakfast.
Sidemen Charity Match 2026: Who is playing?
Sidemen FC
Manager: Jack Joseph
0 – Deji
3 – Marlon
4 – Zerkaa
7 – Arthur TV
9 – Aminematue
10 – ChrisMD
12 – xQc
14 – Adapt
19 – Jynxzi
21 – TBJZL
22 – Niko
23 – AB
30 – AJ Shabeel
61 – LazarBeam
67 – Lacy
77 – Wroetoshaw
123 – Vikkstar123
YouTube All-Stars
Manager: Calfreezy
1 – Sketch
4 – KSI
5 – CarryMinati
7 – Miniminter
8 – George Clarkey
11 – Ibai
13 – AngryGinge
14 – Squeezie
15 – MrWhoseTheBoss
17 – Nykchazza
22 – Fanum
25 – Behzinga
28 – Danny Aarons
66 – Stable Ronaldo
67 – El Rubius
88 – ItalianBach
99 – Jasontheween
Flagg vows to bring Mavericks back
Despite having some experience – albeit limited – playing the beautiful game growing up, Flagg will likely have to settle for being in the 90,000-strong Wembley crowd cheering on the streamers and creators he grew up watching.
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He will do so knowing that he has wrapped up his rookie campaign in the NBA, after the Mavericks failed to qualify for the 2025-26 postseason after posting a 26-56 losing record.
The 19-year-old featured in 70 games for the Mavericks this season, where he recorded a team-high 21.0 points shooting at a 46.8 per cent clip, along with 6.7 rebounds, 4.5 assists and 1.2 steals per game.
He even drew comparisons to that of all-time basketball great Michael Jordan.
“It was a good season,” Flagg said when asked by Marlon about how he found his debut season in the pros.
“But for us, we didn’t win very much. It’s alright, we’ll get it next year.
“We’ll be back.”
