Patience & Practice

Last night was little man's first night of football practice. Well technically it was just conditioning to prepare him for the actual practices in August... but we're calling it practice.. just because. 
So we get there and there are already about 20 kids out on the field and a bunch of coaches. I tell Drew to go out there with the other kids and pay attention.... He's a little hesitant, but to my surprise, he actually went.
They started off with simple stretches, then went running around the track.... Here's where football takes a HUGE turn for the worse for us.... I had forgotten to bring my chair out to the field with me so I while Drew was out running I decided to go the car and get it. HUGE MISTAKE... 
I wasn't back in my spot on the field when Drew came back and he was devastated... scared and very upset.. tears and all. 
So I tried to calm him down.. he seemed ok so I gave him his water and told him to get back out there with the kids because they were lining up to start drills. 
But it was too late.. Drew was done.. 
The running exhausted him.. then he was scared to death... he had NO desire to go back out there and proceeded to cry and throw a tantrum.... and I became the HORRIBLE Mom... I start threatening to take away every video game he owns... then the entire Wii system... dessert.. and then every toy he owns.... but this kid wasn't giving in.. 
So I decided it was over... we were leaving. 
10 minutes into "practice" and we were done. 
But that just made Drew even more upset. As we start walking to the car his crying gets worse and he's begging to stay (because by this point I've already told him his entire football career is over FOR LIFE). 
I yelled. I said things I shouldn't have. I got frustrated. I had absolutely ZERO patience with my 6 year old. I know this kid like the back of my hand.. even better than that.. I know how he responds to yelling and threats (he doesn't) but I did it any way... I lost my cool.... and I am VERY disgusted and disappointed in my behavior.
When we got home and things settled down a bit we climbed in to bed and had a talk. Drew said that he didn't like the "practice", it was too hard to run that much. He doesn't want to do the practices but still wants to play in the games. I explained that it doesn't work that way.. not just because Mommy says so, but it's reality and the coach would tell him the same thing. 
So now I'm stuck... I'm not sure what to do. 
These conditioning practices are not mandatory, but they are recommended to prepare the kids for the actual practices. Do I let Drew skip the next 2 months of conditioning then show up in August for full on practice 3 times a week and hope it does it... and well? Do I make him go to conditioning even though I know it really probably is too much for his tiny body? Or do we just quit before we even started? 
Drew loves football.. he loves watching it, playing it, playing the video games, wearing the jerseys.. all of it.... except practicing it. 
I think we'll go back to practice next Tuesday and let him give it a try.. talk to the coaches and see what they say... and go from there. 
And in the mean time.... I will practice my patience....