Reading defender John Clarke is out for the season, boss Paul Ince has confirmed.
The 18-year-old has featured four times for the first team since his summer arrival from Port Vale.
He completed the 90 minutes in Carabao Cup defeat to Stevenage, as well as picking up 24 minutes of Championship football.
His biggest moment to date was a stunning block in the final stages of a 1-0 win over Middlesbrough, virtually saving a goal by putting his body on the line.
A Republic of Ireland Under-19s international, the teenager has damaged his knee ligaments and will now be unavailable for the rest of the campaign.
With strict EFL restrictions on squad numbers, due to the embargo, former captain Liam Moore will replace the youngster in the official squad.
Speaking ahead of the Swansea City clash, Ince said: "We have a quota. Liam Moore is back, and it will be like having a new player. He comes in and makes it 25 because John Clarke is out with knee ligaments, so that frees up a place for Liam Moore to come in."
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