I absolutely fucking hate this attitude.
Being a supporter means that you get behind the team, which means that you get behind the players wearing the shirt - whether or not you think they're 'having a shocker' or whether you think they're total crap and you could do a better job.
Whether a player in a particular game - or in every game - doesn't meet your expectation of what his standard should be is irrelevant. You're not a fucking critic. He's playing for Spurs. You get behind him. That's your job.
Its not my job. I don't think I could do a better job. I've also criticised bands I've been to see and food in restaurants. I've been a Spurs fan for decades but if I pay good money I have a right to an opinion.