Chelsea midfielder Mikel Obi has backed Rafael Benitez' rotation policy but says it is hard for Chelsea's players to maintain consistency when they are in and out of the side.
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With Premier League, Europa League and the FA Cup all to play for, Chelsea's squad is stretched to its maximum.
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The Blues on Wednesday travel to Russia seeking to turn their 3-1 home win over Rubin Kazan into an aggregate triumph before returning to London to continue their search for a fifth FA Cup in seven seasons.
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Chelsea, by interim boss Benitez's own admission, were far from their best in their fourth game in eight days against Sunderland, but ground out a 2-1 victory.
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The schedule necessitates rotation, but Mikel believes it has taken a toll on the players' form.
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"You can say some of us are a bit tired," said Mikel, who in January won the African Nations Cup with Nigeria.
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"We knew it was going to be tough with the run of games that we have, so we were kind of prepared for it.
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"The manager is doing his job by rotating the team as well, so it keeps some of the players a bit fresh going into every game.
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"It is hard to maintain that level. You want to keep that rhythm going, that level going, and when sometimes you have been rested and you come back, you kind of lose that rhythm.
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"It is hard to take, but you know it's something that everyone has accepted since the manager came in.
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He said from the start that he was going to rotate the team, so we have to get on with it.
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"It's tough but, hopefully, if we can go through this period of games, still in the top three or four, we are going to be pleased with what we have achieved.
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"The most important thing is the team. If the team keeps doing well, keeps winning, most especially towards the end of this season now, we need everyone, we need to keep playing and winning games.
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"If the team keeps doing that then I am very happy." Chelsea have been in a similar position before - a season of turmoil building to a crescendo - as recently as last season.
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The Blues finished sixth in the Premier League but winning the Champions League in Munich and the FA Cup triumph spared their blushes.
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Their only opportunity for Champions League football next term is through the Premier League this season.
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Mikel is optimistic of success on all three fronts.
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"We have to keep going and believing in what we can do," he said.
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"The battle for the top four has always been tough. We knew it was going to be tough, coming to the business end of the season.
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"Hopefully if we could get a piece of silverware this season we will be very pleased with ourselves.
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"We have to keep going and playing the way we are playing."
Rafa Benitez need to make amends in order to motivate every of his players. They have to experience stable play