Jofra Archer's breach of the bio-secure protocols could have been a "disaster" for England's summer, says director of cricket Ashley Giles.
The pace bowler, 25, was dropped for the second Test against West Indies for visiting his home after the first Test.
All of England's home matches this year are being played behind closed doors and in a bio-secure environment.
"The ripple effect it could have had could have cost us tens of millions of pounds," said Giles.
The coronavirus pandemic has forced England to hold the three-Test series against West Indies, and subsequent tours by Ireland, Pakistan and possibly Australia in secure locations at the Ageas Bowl and Emirates Old Trafford.
Not only has great expense and time gone into those plans, but anything that compromises them could potentially cost the England and Wales Cricket Board (ECB) vast sums in broadcasting revenue.
Giles said: "The potential knock-on effect of this, I don't think he could have fully understood.
"We made it very clear what the protocols mean, but maybe he didn't quite understand what the consequences could be."
After leaving the Ageas Bowl, where England lost the first Test, Archer went to his home in Brighton, before travelling to Manchester for the second Test, which started on Thursday.
Giles said Archer was not at home for a "particularly long period of time" and that he visited someone who has since returned a negative coronavirus test.
On Wednesday evening, Archer told one of the members of the England management team that he went home, and he was subsequently removed from a 13-man squad announced earlier that day.
He must now serve a five-day period of isolation and return two negative coronavirus tests before he can rejoin the England squad.
"There will be a disciplinary process to go through," said former England spinner Giles. "That's ongoing. That's an employment matter and we'll settle that in good time.
"Jofra has demonstrated how sorry he is, but it's clearly very disappointing for the whole group. He's a young man and young men make mistakes, and he's just got to learn from them."
Archer was due to be the only member of the England pace attack retained from the first Test, but with his period of isolation lasting the whole of the second, he may not return for the third, which is also in Manchester.
Asked about Archer's availability to play in the final match of the series, England coach Chris Silverwood told BBC Sport: "There's ongoing conversations and I'll be speaking to Ashley.
"We're speaking to Jofra a lot. The guys will rally round, make sure he's doing alright, phone him, deliver his meals, so we've got all sorts to be doing.
"I've got a feeling he's probably learnt a lot in the past 24 hours. It is something that will be spelt out to him as well."
In Archer's absence, England reached 207-3 on day one at Old Trafford, with Dom Sibley making 86 not out and Ben Stokes an unbeaten 59.