The Brothers Tachibana - S1-E22
Character mistake: The Tachibana twins' play leading to the second goal is called by the commentator as "on the limit of the offside", but that does not make sense; there are a bunch of players in front of them, it does not come close to being offside. (00:06:50)
No Victory in Semi Final - S1-E21
Character mistake: To signal the end of the match, the referee blows the whistle just once instead of three times. (00:10:25)
The Youth National Championship - S1-E17
Character mistake: Matsuyama meets Misaki and asks him with surprise if he's part of the tournament too. But in the previous episode, Matsuyama was aware of that already and mentioned to the rest of the team that since they qualified, they would face him. (00:07:50)
Character mistake: At the tryouts, Tsubasa's teacher approaches coach Shiroyama chatting with surprise about the fact that he is in charge of the new team. But the episode opened with her exactly addressing him as the coach of that team. (00:04:40 - 00:19:45)
No Easy Way - S1-E12
Character mistake: In the first shot of the interior of the stadium, the banner says "We ♥ Nankatu", instead of Nankatsu. (00:03:40)
Character mistake: In the map of South America, the nation of Chile is misspelled as "CHLIE." (00:18:05)
No Easy Way - S1-E12
Character mistake: Nankatsu is referred to as Nankatsu FC, but in the first result the name of the club is spelled Nankatsu (in kanji) S.C. (00:10:55 - 00:13:15)
Character mistake: According to the tactical reading of Tsubasa's dad, Tsubasa's flaw is that he's not used to team play since he's just been playing with the ball on his own from a tender age. Just seconds before, Genzo made the comment that Tsubasa is a clever player that can read the passes of his opponents instantly. So he's both clueless about team play and an expert on it in the space of 30 seconds.
Character mistake: The climactic football match takes place at 2 PM, but the French and Italian dubs have Roberto mention that he's anxious to see how Tsubasa ("Oliver") will play "tonight." (00:06:00)
Character mistake: For being such a football fan, Tsubasa surely keeps poor care of his gear, since he goes everywhere wearing football boots, and the studs are certainly not suited for 24/7 usage on asphalt. Even worse for Genzo, who for no reason walks around the city in his full goalkeeper uniform and boots. He's a professional with a private coach who is very strict. Besides...who would keep goalkeeper gloves off the pitch all the time?
Character mistake: Tsubasa runs with the ball from kick-off, which is not allowed. The player who touches the ball first can't touch it again until another player passes it to him. (00:03:45)
Character mistake: Tsubasa takes part in the 200m dash because, as Ryo says "the runner of our team got injured." The runner? There are many athletes taking part in the contest, but both come from just 2 teams. Also needless to say, the race would have also been invalidated, and yet Tsubasa who showed up with no permission and kicking a ball is proclaimed the winner. (00:07:25)
The Football Is My Best Friend - S1-E4
Character mistake: Everyone is making a sincere effort to avoid touching the ball with their hands for the whole episode, even to the point of getting in late at school, but when the kids are waiting in line behind Ryo peeping into the classroom, a few of them have their hands on the ball. (00:06:45)
Character mistake: Rare instance in this anime, a foul is given when four players from Meiwa tackle Tsubasa at once and hook his foot when he successfully evaded them. In truth though, any referee should have blown the whistle already way before, since the four ganged on Tsubasa throwing themselves at him multiple times before that one, each time sticking their leg out without even aiming at the ball - Tsubasa has to literally duck to avoid one of those tackles.
The Verification Test - S1-E16
Character mistake: Ishizaki bashes (quite literally, hitting him in the head with an angry punch) Morisaki because he did not catch Tsubasa's shot, saying it was easy. Someone drew the shot the wrong way or Ishizaki is a complete idiot - and all his teammates that do not say anything too. Tsubasa's shot was almost impossible to catch.
The Youth National Championship - S1-E17
Character mistake: Ishizaki fails to recognize that the 'giant' he met is a goalkeeper. He was wearing long sleeves, goalkeeper gloves and when he walked away Bruce kept staring at him...and the enormous number 1 on his back. It takes a very special kind of football player to not identify someone like that as a goalkeeper.