Arsenal will go into Sunday’s top-of-the-table Premier League encounter with Chelsea in fine form, but have a major fitness doubt over center-back Per Mertesacker. Arsène Wenger’s men won their ninth consecutive match in all competitions last week when they edged past Reading in the FA Cup semifinals.

Yet the victory came at a cost with their German World Cup winner lost to injury in the second half at Wembley, and Wenger revealed that Mertesacker is still struggling with a nagging ankle problem.

“He’s still in the treatment room and I don’t know if he will be available or not,” he said in his pre-match press conference on Thursday. “[He is] 50/50 [to start] at the moment, he has not practiced at all. Apart from Mertesacker, everybody else [from last weekend] should be available.”

If Mertesacker doesn’t make it, Arsenal have a ready-made replacement in Gabriel Paulista. The Brazilian arrived from Villarreal in the January transfer window to provide reinforcement to Arsenal’s sparse defensive options. His appearance as a substitute against Reading was his seventh in an Arsenal shirt, and Wenger insisted he has no doubts about starting the 24-year-old in such a big game.

“He is ready,” he said. “He came on last Saturday and if Per is not ready Gabriel will start.”

Arsenal will go into Sunday’s matchup at the Emirates Stadium 10 points behind leaders Chelsea. And, with only six matches remaining, even a victory for the Gunners would see their chances to claim the title remain extremely slim. A win for Chelsea, meanwhile, would leave Jose Mourinho’s side requiring just two more points to seal the championship.

Yet Arsenal’s form since the turn of the year puts them top of a Premier League table in 2015. And Wenger has again put the contrast in Arsenal’s performances between the first and second half of the season down to injuries.

“We had a disturbed post-World Cup start to the season and we lost too many players to find a good balance. But since January we have done very well so we would like the championship to go on with 10 more games to go now.”

Arsenal now have just two players still unavailable. Captain Mikel Arteta is back in training after undergoing ankle surgery in January, but will not be thrown back into the first-team picture against Chelsea.

“He’s getting closer,” Wenger said. “He’s back in full training still a bit short physically to go into a game of that intensity.”

Meanwhile, Alex Oxlade-Chamberlain is the only squad member still on the treatment table as he continues his recovery from a groin injury suffered in Arsenal’s 2-1 victory over Manchester United in the FA Cup quarterfinals last month.

“He’s still out, he’s not even been in training,” Wenger explained. “He’s not been considered at all.”