James Anderson could be ruled out of the remainder of the Investec Ashes after being forced off the field at Edgbaston with an apparent side strain.
Anderson, England's record wicket taker, was two balls into his ninth over when he clutched his side after delivery. While he bowled one more ball, he then pulled up in his run-up and left the field. His over was completed by Joe Root.
The ECB released a statement on Twitter confirming that Anderson had a "tight side" and would be "assessed overnight". That means he will be sent for a scan with any firm decision about his future involvement delayed until the results are known. The fourth Test begins at Trent Bridge next Thursday.
"I've heard nothing yet," said Steven Finn, who was England's best bowler on the day with five wickets. "Obviously pulling up halfway through an over for someone like Jimmy, he wouldn't go off if it wasn't hurting.
"He's a huge player for us. He is the leader of our attack. He sets the tone with everything he does. Jimmy loves bowling at Trent Bridge, everyone knows that. If he was to miss it, it would be a big loss, but we don't know yet."
The injury took the gloss off an otherwise wonderful day for England. While they are strong favourites to take a 2-1 lead, the loss of Anderson would be a major blow. Anderson has a superb record at Trent Bridge: he has taken 53 wickets in eight Tests on the ground at an average of 19.24. He claimed a 10-wicket haul in the last Ashes Test there in 2013 - one of two 10-wicket hauls he has at the venue - and has taken six five-wicket hauls there.
If Anderson is unavailable, as looks likely, England will probably look to Mark Wood to take his place, though Mark Footitt and Chris Woakes may also be considered.
England, meanwhile, only have eyes for tomorrow's third day, when Australia will resume with a lead of 23 and three wickets in hand.
"The game is most definitely still not won yet," said Finn. "They've got guys to come in who can bat, there will still be pressure on tomorrow and we have to do a professional job."