If you're right about Barry not being able to last 90mins then we've made a big mistake giving him a 3year contract! I'm hoping as the season goes on his stamina will improve.
I don't think the three year contract is a mistake in itself. If we use him correctly he could still perform to very good level for at least another 18 months, and we might recoup some of the transfer fee by selling him on to an MLS club in the states.
The mistake will be expecting Barry to play 90 minutes, week in week out, for a season that could potentially be sixty games long. Every player has a finite level of fitness, and age takes it's toll. In our formation we use two CDMs and it's generally agreed that we have four senior players for those positions: Barry, McCarthy, Gibson and Besic. It follows that in any game, two of them will start and a third will be on the bench - it is important this season for us to rotate our starters and to use our bench options in order to keep everyone as fresh as possible, but so far Martinez has not done that for the CDMs.
Leicester: Barry and McCarthy start, both play entire game. Both tire visibly (along with most of the team) as game progresses, and Barry picks up a yellow for a poor challenge as his pace and positioning let him down. Generally agreed to be lucky to stay on the pitch as more fouls follow. Leicester look fitter and stronger as the game gets into the final 30 minutes and we start to lose the battle in midfield. Martinez only uses two subs, both coming on in the last ten minutes - neither is a CDM, Besic is on the bench but is not used.
Arsenal: Barry and McCarthy start, both play entire game. Both tire visibly (along with most of the team) as game progresses but in fairness they dominate Arsenal in the first half. Arsenal look fitter and stronger as the game gets into the final 30 minutes and we start to lose the battle in midfield to the extent that rather than compete there we drop back and defend deep, inviting pressure. Their first goal is scored by a midfielder, Ramsey, coming from deep with no-one tracking him - he's by no means the most advanced attacking player, so our CBs appear to be concentrating on Giroud, Cazorla and Campbell, all three of whom came on as substitutes and took up very attacking positions. Martinez uses all three subs, but two come on in the last fifteen minutes. None of the three is a CDM, Besic is on the bench but is not used.
Chelsea: Barry and McCarthy start, both play entire game. Barry visibly tired on 60 mins, totally ineffective by 70 mins. McCarthy covers more and more ground as game progresses, tiring noticeably in the process. Chelsea score three late goals as our defence is left exposed by two shattered CDMs. Martinez only uses two subs, the second one coming on with three minutes left in the game.
Summary: Barry and McCarthy started the season below optimum fitness (like almost everyone) and have played every minute since. Barry particularly has struggled with this, evidenced by the fact that by the time Chelsea are scoring their fourth goal, he is moving at a walking pace despite the ball being passed through his area of responsibility just outside the box. By failing to close Matic down he allows the Chelsea man to advance with the ball and line up a shot between Distin and Jags. For the fifth goal many have been pointing the finger at McCarthy for not tracking Ramires but why is McCarthy having to defend on Barry's side of the field in the first place? I think it might be because Barry was unable to cover the ground and get there.
It's foolish to not rotate when we have the squad to do it. All three subs should have been used against Leicester and Chelsea, but they weren't. Only one of our substitutions this season has been made with MORE than fifteen minutes left to play, despite several players looking completely spent after 60 minutes in each game. And that one was because of injury.
We've run the same two of our CDMs into the ground in three successive games and paid the price three times. One of our backup CDMs has been on the bench for all three games, and played a sum total of about six minutes.