Squad rotation is a good thing. I don't think there are too many fans or pundits that would argue that. The reason that squad rotation is such a vital thing to utilize is to keep players fit and fresh, and with that in mind, yesterday was a complete and utter failure by interim manager Rafa Benitez.
The holiday period is always busy, especially so for Chelsea this season with the Club World Cup. Players will need rest, and the manager needs to be keenly aware of that fact. Rafa Benitez talks about tired players enough that we know he is, in fact, aware that the players were tired. As a "top level" manager though, he needs to be able to prioritize games properly and assure that he fields lineups capable of winning the more important games, even if it means potentially sacrificing a trophy like the League Cup or Club World Cup to do so.
There are some things yesterday that Rafa couldn't do too much about. Fernando Torres is obviously tired, but there just aren't many real options to give him a rest yet. With John Obi Mikel, John Terry, and Oriol Romeu injured, there just won't be much rest for Gary Cahill, Branislav Ivanovic, or David Luiz. Again, there isn't too much that he'll be able to do there until some reinforcements arrive.
There are several areas where Chelsea have depth and quality though, and his mismanagement of these positions was disgustingly evident in yesterday's loss. Not many would argue that the two best players at the club are Juan Mata and Eden Hazard, and they both happen to play in the deepest position at Chelsea. Giving one or the other a rest should not be too difficult, so much so that needing to rest both due to accumulated fatigue during the same Premier League game at any point is absolutely inexcusable.
What makes it even less excusable is the fact that there are two perfect fixtures coming up in which to rest both players. The League Cup and FA Cup are both luxury competitions for most, and a club that still had some sort of reasonable title hopes as well as a real fight for Champions League qualification should never be resting their two best players at the same time due to fatigue with a potential 10-day break just 90 minutes away. Rafa had the ability to rest Mata at least once since the Manchester City game, he should have foreseen this issue and done so during a game that Hazard was able to start.
We knew about these congested Premier League fixtures when Rafa took over, and it would have seemed appropriate to start planning for this exact situation during the Club World Cup and League Cup game against Leeds. Instead the pair played a combined 456 minutes during that three-game span, and neither of the pair have been give a full game off in any of the matches since then. Maybe sitting one down before 75 minutes of the Aston Villa affair would have been a good idea Rafa?
What makes things worse in my mind is the decision making involving Ashley Cole. Yes, Cole is getting older and will need rest more often. Failing to plan for that fact so that Cole misses out on the same day as you need to sit both of your best attacking players just compounds the situation. It's ludicrous, and it's probably the biggest reason the squad looked so disjointed yesterday.
Rotating the squad was supposed to be one of Rafa Benitez's strengths when he was brought in to replace Roberto Di Matteo, but the lineup he put out yesterday shows he's got to do some serious rethinking of his rotation policy. Playing the backups is good for the squad, playing most of your backups in place of the bulk of your best players in the same game is idiocy of the highest order. Prioritize games appropriately, and rest players accordingly. That sort of thing should help to avoid results like yesterday in the future.