flay

The fact that they're even willing to create this fight implies that Saitama could lose, and that alone is ridiculous. Moreover, the series is called One Punch Man because that's what Saitama does. Goku has taken damage from people far below his level, so why should we believe he would survive a punch from a guy who terraformed the moon just by jumping back to Earth? The canonicity of Dragon Ball itself is all the evidence you need to know how this fight would normally go down, as it presents Goku as being fallible, which is the exact opposite of Saitama.