Neil Warnock reacts as defender leaves Middlesbrough ahead of Reading, Cardiff City and Sheffield Wednesday fixtures

The 31-year-old saw his contract expire on June 30 but agreed to sign a short-term extension to complete the campaign.

Shotton returned to Boro’s starting XI at Millwall last week before producing a man of the match performance during a 2-0 win at The Den.

Yet the experienced defender was forced off with an injury during Saturday’s 3-1 defeat by Bristol City, meaning he won’t be fit enough to finish the season with the Teessiders.

Shotton will therefore miss Boro’s remaining fixtures against Reading, Cardiff City and Sheffield Wednesday.

Boro boss Neil Warnock said: “Ryan was absolutely fantastic against Millwall last week and he gave us everything against Bristol City at the weekend.

“He was feeling an injury during the second half so we brought him off because we didn’t want to make it worse.

“This is our third game in less than a week and Ryan wouldn’t have played against Reading.

“With him not being 100 per cent fit, he feels vulnerable to an injury that could prevent him getting him a contract elsewhere. I’m disappointed, but I fully understand his thinking.”

Shotton has made 84 appearances for Boro after joining the club in August 2017 from Birmingham City.

The defender’s departure meant the Teessiders were only able to name eight substitutes at Reading as midfielder Ravel Morrision missed out through illness.