Chelsea's handling of Thibaut Courtois's head injury in Sunday's win over Arsenal has been criticised by brain injury charity Headway.
The goalkeeper collided with Alexis Sanchez, but played on for 14 minutes before going to hospital for checks.
Headway chief executive Peter McCabe said it was "hard to understand how a concussion was not suspected".
Chelsea defended their actions, saying Courtois, 22, had suffered "a minor cut to the ear".
Courtois tweeted on Monday: "Thanks for all the messages! I'm already feeling better. Now I'm resting to be recovered and back on the pitch soon. Great victory yesterday."
Under Premier League rules introduced this season, players must leave the pitch after suffering a head injury.
|New concussion measures this season|
|A player suffering a head injury must leave the pitch.|
|Team managers or coaching staff will no longer decide if a player continues to play. The final decision will be with the club doctor.|
|Home teams in the Premier League must now have a third "tunnel" doctor on match-days to support doctors for both sides.|
|The "tunnel" doctor will help to spot potential concussions and watch TV replays to judge the severity of incidents.|
|All Premier League players will undergo baseline neurological assessments as part of their annual medical check-up to help doctors measure their recovery time if they suffer a concussion.|
Courtois was injured in the 10th minute at Stamford Bridge. After being assessed on the pitch by Chelsea medical staff, he continued until the 24th minute, when he was replaced by Petr Cech.
Television pictures appeared to show Belgium international Courtois bleeding from an ear as he was substituted.
"The new rules introduced this season were designed to ensure no risks to players' health were taken," McCabe said in a statement.
"They clearly state that 'if there is any suspicion of the player having sustained a concussion, they must be removed from the field of play, and not allowed to return'.
"Bleeding from one or both ears is one of the symptoms that requires an immediate visit to hospital."
A Chelsea spokesman told BBC Sport: "Thibaut Courtois went to hospital during our game against Arsenal yesterday for precautionary tests on a head injury.
"Those tests came back all clear. He is expected to report for international duty later this week."
Belgium boss Marc Wilmots later confirmed on Twitter that Courtois would join up with the national team on Wednesday ahead of their Euro 2016 qualifying matches against Andorra on Friday and Bosnia-Herzegovina next Monday.
Blues manager Jose Mourinho said after the match he was happy to defer to the expertise of his medical team.
"They gave me the decision and for me, that's correct - the club doctor or the club medical department to take control and take responsibility," Mourinho said.
Last season, Headway said Tottenham were "irresponsible" for letting keeper Hugo Lloris play on after he lost consciousness against Everton.
Chelsea beat Arsenal 2-0 thanks to Eden Hazard's first-half penalty and a late Diego Costa strike to restore their five-point lead at the top of the Premier League.