3T Madara's best feat in this department was slaughtering a bunch of fodders, which is something base Gai has already done back in part one against the sound ninja. Madara is fast, but not that fast. Gaara had no problem following his movements, and blocking his strike with sand [
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]. Base Gai is fast and skilled enough to effectively hop in a CQC fight amongst Rinnegan Obito and KCM Naruto - successfully combating the former who was using Kamui. Gai has already countered the Gunbai with his nunchucks coming from a complete blind spot, and his durability will not be easy for Madara to get around (DB hyped to be as strong as steel, and withstanding a direct super human strength punch). Now add on the stat boost of the 3rd gate, which also provides access to the lethal Ura Renge, and 3T Madara is not winning with a Gunbai and taijutsu alone.