Great Britain Hockey coach Danny Kerry confirmed captain Kate Walsh had been taken to hospital after being hit in the face late in their 4-0 win over Japan.
However, he does not yet know how serious the injury is and it is likely an update on her condition will not be given until Monday. The 32-year-old, the team's most experienced player, was caught on the left side of her jaw by a full swing by Akane Shibata and left the pitch with blood coming from her mouth.
"She's with the medical people and we are awaiting further information," said Kerry. "She has gone to hospital to be checked out."
The injury to Walsh was the only downside to a comprehensive victory as midfielder Helen Richardson came off after taking a ball to the kneecap but is expected to recover in time for Tuesday's match against South Korea.
Striker Alex Danson grabbed the headlines with two goals either side of strikes from Wales international Sarah Thomas and Sally Walton.The Reading forward was returning to the venue for a competitive match for the first time since May when she was forced off with a dislocated shoulder in the final of the Olympic test event, which GB won.
"To come out and win our first game was exactly what we dreamed of and have worked towards," Danson told Press Association Sport. "It was incredible to score. I can't believe I'm at home and my family are watching but if I'm completely honest I don't mind who scores, as long as we score one more than the opposition.
"We celebrate the goals because we have spent hours practising so when we score you get the feeling it is working. I guess it is different now because this is where we now want to be.
"I had a scare at the test event and it was more the feeling of not being part of something incredibly special which worried me. It is difficult to explain how it feels when I line-up with my team-mates because you just want to do so well for the next person. So the thought of not being part of that was most devastating. To be here is the greatest thing I could be given."
Kerry was satisfied with the way the game panned out, even if they could not add to their first-half tally.
"I thought we controlled the game and took our chances in the first half and in the second half it was all about not being gung-ho and retaining that control," he added. "It was a very thorough and diligent performance. It was the first time the girls had played in front of the full 16,000 here and they weren't affected in any shape or form."