London - England fullback Mike Brown is still suffering concussion symptoms after sustaining a head injury against Italy in the Six Nations, head coach Stuart Lancaster revealed on Tuesday.
The Harlequins player took a heavy blow to the head during England's 47-17 victory at Twickenham on Saturday and faces a race against time to prove his fitness for the showdown with Ireland in Dublin on March 1.
"We're going to have to see how he comes through the return-to-play protocols. He'll go through that graduated return and he hasn't started that yet," Lancaster told a press conference.
"He won't take any part in training this week. So if he starts all that tomorrow (Wednesday), then he goes through that process, so that would be from the bike and onwards.
"Seven days would give him enough time in the build-up, but that's hypothetical at the moment because he hasn't started the process, so we'll wait and see."
Brown can only return to training once he has not displayed any concussion symptoms for 24 hours.
England have released 17 players to play English Premiership rugby this weekend, but forwards Courtney Lawes, Geoff Parling and Tom Wood are not expected to play due to injury.
"Geoff Parling, Tom Wood and Courtney Lawes still haven't trained fully yet, so it's unlikely they'll be available this weekend for the clubs," said Lancaster.
"But they should all be available to train fully next week. Then obviously a decision needs to be made from our point of view whether to include them in our squad for Ireland."