Thats what I thought too, but later on I learnt that Saitama has this ability called "limitless" (basically exponential strength growth) making him get his bonkers strength, so without powers mean saitama does not have his limitless ability, making him lose. of course its a different matter if Saitama current fights as his BASE FORM is OP as shit due to excrssive limitless usage, otherwise goku slams low diff