Arsenal boss Mikel Arteta is unsure when Takehiro Tomiyasu will be ready for a playing return.
Right-back Tomiyasu, who established himself as first choice following his summer arrival from Bologna, has missed Arsenal's last five games after aggravating a calf problem, with Cedric Soares's deputising ably.
The defender appeared to be over the issue that has troubled him for the last couple of months when he returned for Arsenal's Carabao Cup semi-final second leg against Liverpool but Arteta fears he may have come back before he was fully ready.
Arteta said: "He had a calf injury and after that he had a really quick recovery, we play him, maybe too quick I don't know.
"He had a recurring injury there and then he felt it again one day when he was back in training with us so yes, disappointment because he has been really important.
"He played a lot of minutes, he played quality minutes and had a good contribution in the team and unfortunately now we cannot use him.
"It's good to have someone like Cedric that when we had to use him he was ready because he is a great professional and he is performing well for the team."
Asked when Tomiyasu may be back, Arteta added: "I don't know. He needs to be consistently training for a period [so] that we can minimise the risk of having another recurring injury in the same muscle because it would be something to worry about and we have to stay away from that."
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