Championship play-off chasers Middlesbrough rocked by news that key defender is out for rest of the season

The Republic of Ireland international, 29, a consistent figure in the heart of their backline since joining the club in the summer of 2022 from second-tier rivals Blackburn Rovers, has been sidelined since Boro’s first league win of the season against Southampton on September 23.

Lenihan had found the net in Boro’s 1-1 draw against Sheffield Wednesday four days earlier.

Despite Lenihan rehabilitating for a spell in a bid to clear up the problem, the injury issue has not improved and he has now revealed on Instagram that he has undergone surgery and will not play again this season.

He wrote: "Road to recovery begins today after undergoing a successful operation.

"Gutted to be missing the rest of the season, but I’ll be helping the lads as best I can from afar."

The news that Lenihan has gone under the knife is an untimely development for the Teessiders, who have transformed their season in remarkable fashion in the second half of the autumn.

Michael Carrick’s side propped up the table on goal difference after their draw against the Owls just over two months ago – they failed to win in their opening seven league games of 2023-24 and took just two points from a possible 21.

In nine second-tier matches since, Boro have won seven games and lost only once and taken 22 points from the last 27 available to move up to tenth place in the table.

They are currently just two points behind the side who are occupying the final play-off place in Sunderland.

Lenihan is the second senior Boro defender to be ruled out for the rest of the campaign, with Tommy Smith also out with a serious ankle injury sustained in the win against Birmingham City last month.

Major summer loan signing Lewis O'Brien is also currently out of action with an ankle issue.

The development regarding Lenihan leaves the club light in terms of their central defensive options.

The Teessiders, pushing for a play-off place alongside East coast rivals Hull City, return to action following the international break at Bristol City this weekend.

After hosting Preston North End to end November next Tuesday, they make the visit to Elland Road to face Leeds United on December 2.

Boro also face Hull next month in a televised game at the Riverside on December 13 and visit Rotherham United and Huddersfield Town over Christmas.