Middlesbrough’s Premier League promotion push has taken a controversial turn with the club triggering an English Football League investigation into an alleged Southampton spy at their training ground ahead of the first leg of their promotion playoff semi-final.

Ahead of the clash at the Riverside Stadium on Saturday, BBC are reporting that Southampton’s performance analyst was allegedly caught filming and taking pictures of the tactical session.

In a statement, the EFL have said: “The EFL has written to Southampton FC requesting their observations following a complaint from Middlesbrough FC relating to alleged unauthorised filming ahead of the two clubs meeting in Saturday’s Championship play-off semi-final first leg.

“The alleged incident is said to have taken place on Middlesbrough’s private property by an individual identified to be associated with Southampton.

“The League is treating this matter as potential misconduct under EFL regulations and will be making no further comment at this time.”

Under EFL rules, there is a 72 hour window where clubs are not allowed to observe their rivals’ training sessions.

It sparks memories of when Marcelo Bielsa sent a Leeds staff member to look at Derby’s training ground ahead of a game in 2019. The club was fined $376,000.

Meanwhile, Socceroos star Riley McGree has been declared fit to play by his boss Kim Helberg as the countdown to the playoff ramps up.

Southampton head coach Tonda Eckert knows his side will have to stem Middlesbrough’s flow at the Riverside if they are to take something from the first leg of their Championship play-off semi-final.

The Saints are the form team following a 19-match league unbeaten run which pushed them up into fourth place, having almost gatecrashed the top two with a late surge.

Middlesbrough, meanwhile, saw their automatic promotion hopes checked after managing just two wins from their final 10 games.

Having watched his side slump to a 4-0 defeat to ‘Boro on Teesside back in January, Eckert will not be underestimating the challenge posed by Kim Hellberg’s men in Saturday’s 12.30pm kick-off.

“They have been quite clear in the way they approach the game. I think it is quite clear to see where they have their strengths,” Eckert said at a press conference.

“If they catch a good day and they start to flow, I think they are a good team in certain aspects of the game.

“(But) we come from some good weeks and months. In the end it is about getting our strengths on the pitch like we have been doing for many, many weeks now.”

With the second leg at St Mary’s on Tuesday night, the Saints could be forgiven for thinking heading back down south with a draw would not be a bad result.

Eckert, though, insists that will not be in his team’s mindset.

“No, that is not the way we approach games,” he said. “At no part of the season has that ever been our approach to draw a game. We will go there to win.”

“We will do everything to win, and then we will see where we stand.”

The Press Association contributed to this report