Gareth Bale was forced off at half-time of England's 3-0 win over Wales with a hamstring injury.
The former Real Madrid forward played the full 90 minutes of Wales' other World Cup group matches against the USA and Iran but came off early against the Three Lions on Tuesday.
The Dragon's captain failed to return from the dressing room at half time at the Ahmed bin Ali Stadium and was replaced by Nottingham Forest forward Brennan Johnson. Wales boss Page explained why he had to take Bale off at the break, telling BBC Sport: "[Bale] tried to get to half time but unfortunately, he felt his hamstring. Look at Joe Allen, first 90 minutes for ages and he's thrown everything at it. Ben Davies had to come off through injury. It was a massive effort from the group and I'm so proud of them."
England took the lead against Wales early into the second half after a goalless first 45 minutes on Tuesday night.
Marcus Rashford opened the scoring for the Three Lions with a well-struck free-kick - the first direct set piece to hit the back of the net in the tournament to this point.
Manchester City's Phil Foden, in his first start for England this World Cup, made it 2-0 just a minute later before Rashford made it three.
Wales boss Page admitted ahead of the England game that he may have to use Bale sparingly in his nation's final group match due to his age.
He said of the 33-year-old before kick-off: "It's a big ask for anybody in this environment to go four days later. I'm going to pick a team that I think can go out and compete against England, whether that's with or without them. I'm not going to give that away.
"If they don't start, can they can make an impact? That's always been my dilemma playing games in quick succession. If they start one game, can they start the next? My thought process won't be any different.
"Whether they come on and have an impact or start and last an hour or 90 minutes, they are talented footballers. We're all getting criticism now and rightly so because results aren't going our way and that's the industry we're in.
"We're big enough to take it – it's not a problem. We put our big boy pants on and get on with it."
