Factual error: The whole "Did the referee blow his whistle because of the goal, or because the match is over" isn't possible; the referee blows his whistle three times for the end of the match, not just a single time. (However, it should be noted that technically it's a universally adopted convention but not a hard-coded rule). (00:05:50)
Factual error: Ken Wakashimazu, the reserve keeper, just announces a substitution, himself, from the crowd (not even the bench!), his presence unbeknownst to the coach and everyone else in attendance. For those not familiar with the rules of soccer (or ANY sport!), that's really not how it works in an official match. (00:13:30)
Factual error: At cost of stating the obvious; nobody is allowed to enter the pitch on a whim from the stands, even going as far as hitting a player kicking the football at them, it's pitch invasion. Nobody says anything about it and the referee is mysteriously absent though.
Factual error: It's the first leg of a tournament between elementary school players, and people skip work to see it, the city streets are empty because everyone is home watching it (since it is televised, too!)... That just never happens. It is not a world different from our own where everything is based on the sport (like Pokemon).
Factual error: Blanket statement for most of the series; 90% of the tackles and blocks shown in the anime would never fly in a real soccer match. Some are particularly outrageous and deserve separate mention, but in general everyone's defense is careless at best, and downright criminal at their worst. Take Kojiro Hyuga's introduction; his 'dribbling' involves shoving the opponent off and the challenges for the ball end up with the opponents bleeding and with torn socks. Any ref would stop this sort of 'play' right away.
Factual error: The world record for high jump from professional adult athletes is barely above 2 meters when we do not consider the Fosbury flop. An 11 years old kid here nonchalantly leaps over the goal net (which is around 2 meters, close to two and half if they use a professional one, slightly less for junior matches), from a big distance and landing on his feet on top of the bar...and it's just an effortless transition before he does the REALLY impressive stuff. These kids are not supposed to be superhuman. (00:14:50)
Factual error: Wakabayashi is seriously injured and everyone is aware of that and acknowledges it, but no substitution is made. That's criminally irresponsible, especially with the team being in the lead. The referee himself couldn't ignore this in a real match, since the player couldn't even perform a goal kick.
Factual error: If we had to go by the pre-kickoff aerial shot, Shuutetsu is playing with a 2-3-5, which is definitely not a normal soccer formation - and we never see during the actual play anything close to the team having 5 forwards. Also, the linesmen are infield instead of behind the sidelines. (00:17:05)
Factual error: Tsubasa is daydreaming over a picture of Italy winning the 1982 World Cup. The uniform in the photo though has trunks and collars of the wrong color, a yellow that has never been part of any of Italy's sets. And even if it's certainly not a photorealistic cartoon, the features/hairstyles of the team depicted have nothing to do with the winning team; the winning team was not composed of gingers with big perms; the majority had black hair of medium to short length. (00:02:45)
Factual error: During the series it's routine for powerful shoots to rip through the net. Needless to say, that can't happen with human strength. In later seasons there are shots that even leave craters in cement walls. Remember, nobody in this series has superpowers. It's supposed to be dramatic and over exaggerated in how the whole pitch feats play out, but those holes in the wall are real.
Factual error: In this episode we have a random person showing up and being admitted to the team and playing as substitute on the spot, with nobody protesting. He puts on the (sweat-soaked, presumably!) uniform of another player and just goes ahead without any check from the referee or assistants. Given that the match is between two schools without necessarily having the official football federation involved, it is understandable, but they do not even ask the opposing coach if they are OK with something so obviously outside of any established rule. And they are still playing in a packed stadium, with official referees and even a radio commentator! Only in anime.