Arsenal goalkeeper Lukasz Fabianski could be set for another extended spell on the sidelines with a rib injury, manager Arsene Wenger has confirmed.
The Poland keeper had only just returned to the side following fitness problems, ousting countrymen Wojciech Szczesny as he delivered a clean sheet in the Champions League away win over Bayern Munich and then also at Swansea.
However, Fabianski missed the midweek goalless draw against Everton at the Emirates Stadium, and is now set to be monitored "day-by-day" to assess his availability for the crucial run-in as Arsenal look to cement a top-four finish.
"Fabianski has a crack in his rib that has not moved, so we have to treat it clinically,'' said Wenger, whose side travel to Fulham on Saturday.
"That means has he pain or does he not? That is day by day."
Szczesny, who turned 23 today, coincidentally sharing a birthday with his Polish team-mate, had little to do against Everton, but was alert enough when called up.
Wenger was happy with the goalkeeper's response to being dropped - which had brought stinging public criticism from the player's father.
"He had a good performance, I was pleased with his focus, with his sharpness," the Arsenal boss said.
"He dealt well with the situation that he faced.
"In our job there is only one way to respond, to practice harder and stronger and show that you are ready for a fight, that is what he did.''
Wenger felt referee Neil Swarbrick should have taken a firmer stance against what was some tough tackling by Everton on Tuesday night, when midfielder Darron Gibson stayed on the pitch despite twice pole-axing Theo Walcott.
The physical approach of some players was again highlighted in the Premier League game between Manchester United and West Ham at Upton Park, where Andy Carroll clattered into goalkeeper David De Gea in a challenge which Red Devils boss Sir Alex Ferguson claimed should have resulted in a red card.
Wenger admitted he could see both sides, adding: "He went for the ball at the start, but he was too late.''
However, the Arsenal manager insists robust challenges are "a strength of the English game".
Wenger continued: "For me it is more the intention of the player that counts. When a player makes a deliberate foul to stop a player going forward on a counter attack, that is a real yellow card.
"After, the physicality of the English game is one of the attractions of it, as long as the intention is fair from the player who goes into the challenge. That is the most important.
"What we have seen recently, and what you sometimes only see on slow motion, is players who go over the ball.
"I don't have a problem with players who go in completely 100 per cent because that is what you want to keep in the English game.
"Sometimes I watch foreign games and after 20 minutes you are bored because every time somebody goes down it is a foul, and you say 'Come on'. That is not football as well.
"We do not want to lose the strengths and what makes English football attractive, but the intention of the players has to be fair.''
After Chelsea beat west London rivals Fulham 3-0 at Stamford Bridge, Arsenal are now back down to fourth again, a point behind the Blues and two ahead of Tottenham, albeit having played a match more.
Wenger expects nothing else than total commitment when they travel to Craven Cottage, chasing what would be a ninth win in the last 12 league games.
"We are in a fight where every performance you want to be at the best possible level and we will focus on that on Saturday,'' he said.
"It is a derby and you always expect a game in London to be difficult so the only for us to deal with that is to focus the way we did against Everton and come out with a strong performance.''
Wenger, meanwhile, played down suggestions he was set to move for Alex Song in the summer, following reports the combative Cameroon midfielder was unhappy with life at Barcelona, having signed a five-year deal after a £15million transfer in August.
"There is no buy-back [clause] in his contract,'' said Wenger.
"He is a quality player and sometimes the players have to insist when it doesn't go well and not change his mind too soon.
"My personal advice for him would be to give it another go and after two seasons he can still make a decision.''