Most demanding positions over the length of a Season?

I am gonna assume that your talking about college or higher and I think your pretty close, other than adding a over worked closer. But then you have to consider guy's like Harper and Trout who play very hard every day and their bodies pay the price.

 Since this is a HS forum, I would think that a good SS with a big arm is subject to overwork. I have seen coaches use this guy to close a ball game, and come back the next day and throw a complete game. Quietly racking up 150-175 pitches a week and playing SS at the same time. This scenario would also work for a 3b also.

What a great question and great topic for the transition to college baseball.

Before I would get to position, I would start with the level within the school.  No matter what position, most freshman wear down at a much more rapid rate.  It is not a fault, but learning to manage classes, diet, baseball and the rigors of each especially with the travel of a college season. The combination and "stress"  leaves most 1st year players exhausted in ways they never envisioned. If we build a Summer Wood bat league on top of the college season, the season itself takes a huge toll, no matter what the position.

Once the adjustment to college is hopefully made by the sophomore season, I think your views are pretty solid. On the other hand, I think a junior shortstop who knows what is coming is in far better shape and wears down less, because he is starting from a different level.  Catcher, for sure, has to be the toughest.

The obvious answer is catcher.  However the majority of injuries, and I might add season ending injuries, are suffered by pitchers.

In HS (Virginia) it was very rare for my son's team to play back-to-back in succusive day unless due to weather.  Most weeks had games on Tuesdays and Fridays.  Occasionally a Wednesday or Thursday game was thrown in.

Yes.  At my son's JuCo the coach alternates catchers during doubleheaders.  56 games does take its toll.

gitnby, it is a grind. That is the one thing my son learned his first year of Juco. The thing he took away from that season was to try to keep the weight on and maintaining muscle. He dropped close to 18-20 lbs that season. By keeping the weight up he is able to maintain his muscle and thus able to keep up the pace of the demands of the season. He is a thirdbasemen

The college season is extremely demanding. Juggling school and the demands of baseball is no small feat.

My son realized that every season during finals week his team's baseball performance would dip, since they would basically be working with 3-5 hours sleep each night for two weeks. There is just no way to keep this from being reflected in their performance on the field. He hated it. He really resented the school portion of being a student athlete at those times.

Then, when he finished college and played his first pro season, he stacked 70 games on top of the 56 college games. By early August, his legs were very tired. He really had to learn how to play through the fatigue, and how to eat, rest, and train to withstand the demands.

What an experience that was, figuring out how to play 31 games in 30 days in July in the midwest, as a first year pro.

And guess what? The MLB guys have a 162 game season! This is not easy! This is a hard way to make a living!