Captain Owen Farrell could miss the start of England's Rugby World Cup campaign after he was sent off in a come-from behind 19-17 warm-up win over Wales at Twickenham on Saturday.
The fly-half was initially shown a yellow card for a high tackle to the head of Wales replacement Taine Basham in the final quarter.
But under new rules that allow a review panel to consider an act of foul play while the game is in progress, that was soon upgraded to a red.
When Farrell left the field, it meant England, who kicked off close to full strength, were briefly down to 12 men with replacement prop Ellis Genge and full-back Freddie Steward having been shown yellow cards as well.
But England overhauled a 17-9 deficit thanks to Maro Itoje's converted try from a driving maul and a late penalty from replacement George Ford as they avoided a fourth successive defeat and a slump to ninth in the world rankings.
England have two more warm-up games, against Ireland and Fiji.
Any suspension could rule talisman Farrell out of the start of the World Cup, with Steve Borthwick's team launching their Pool D campaign against Argentina in Marseille on September 9.
Farrell's three-match ban for a similar offence in January may now count against him in any disciplinary hearing.
Adding to England's concerns was an ankle injury suffered by scrum-half Jack van Poortvliet, with the Wales trio of captain Dewi Lake, Taine Plumtree and Basham all going off injured as well.
"Regarding Owen, we'll wait and see what happens," England coach Borthwick told Amazon Prime. "The same with Jack van Poortvliet, he'll get a scan. Rather than jump to any conclusions, we'll wait and see what happens."
England were largely lacklustre behind the scrum but former captain Borthwick said: "The attack is the final building block and takes the longest to come, but that's what we're working on."
Earlier this week, Borthwick unveiled his World Cup squad, but Wales boss Warren Gatland has still to decide on his 33-man party for the showpiece tournament in France.
- 'Furious' Gatland -
An angry Gatland, who made 15 changes to the Wales team that beat England 20-9 last weekend in Cardiff, gave some of his side an ominous warning about their World Cup chances.
"I am furious actually, I am hugely disappointed but we found out about a few people today," he said.
The New Zealander, who twice led Wales to fourth-place finishes in the World Cup during his first spell in charge, added: "That was a game we should have won and we cost it ourselves."
England were 9-0 ahead early in the second half of an error-strewn match thanks to three Farrell penalties before Owen Williams responded with one for Wales.
But from 9-3 up, England found themselves struggling following three yellow cards.
Genge was sin-binned for collapsing a scrum, minutes after coming off the bench to win his 50th cap, with Steward shown a yellow card for taking out wing Josh Adams and Wales awarded a penalty try for the full-back's subsequent tackle on Liam Williams that prevented a certain score.
Wales capitalised, with Tomos Williams's converted try putting them 17-9 ahead only for England to rally late on.
England face Six Nations Grand Slam champions Ireland in a Dublin warm-up a week on Saturday, when Wales continue their preparations at home to World Cup holders South Africa.
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