Leeds United face wait over Adam Forshaw and Pontus Jansson with Jamie Shackleton set to retain Whites place

Forshaw pulled a hamstring in Leeds’ 1-0 win at Derby County on Saturday and is expected to sit out the return fixture at Elland Road as United attempt to secure passage to Wembley.

Bielsa went with the former Middlesbrough midfielder’s experience at Pride Park but turned to Shackleton in the 24th minute after Forshaw pulled up in the centre circle.

Shackleton responded with a strong display to help Leeds claim in the initiative over Frank Lampard’s side and put themselves within 90 minutes of an appearance in the play-off final.

Bielsa had already lost centre-back Pontus Jansson to an ankle injury before kick-off, bringing Gaetano Berardi into Leeds’ starting line-up, and his bench was so short of proven players that three of his substitutes - Under-23s Mateusz Bogusz, Robbie Gotts and Pascal Struijk - were without a senior appearance between them.

Asked whether Forshaw or Jansson would make Wednesday’s second leg, Bielsa said: “Forshaw I don't think so. For Pontus Jansson I couldn't tell you yet.”

Jansson was a pre-match doubt having missed training on Thursday and Friday but a convincing display from Berardi, in a defence which denied Derby a single effort on target, could also keep him in Bielsa’s line-up for a sell-out second leg at Elland Road.

Shackleton, meanwhile, is in his maiden season as a first-team player but had been limited to three starts and 16 substitute appearances before Saturday, despite impressing consistently on the occasions when Bielsa used him.

The 19-year-old hassled Derby with his running and movement and came close to doubling United’s lead late in the game when his volley was clawed away by County goalkeeper Kelle Roos.

Bielsa said: “He showed his character and personality and he adapted immediately to the game. He defended well and he attacked well.

“The fact that we lost Forshaw could have had a big influence during the game but Shackleton was very efficient.”

The United boss also reserved praise for Jack Harrison and Kemar Roofe, who combined in the 55th minute at Pride Park to force the only goal of the game.

Roofe was on hand to tuck away a pin-point cross from Harrison, claiming his 15th goal of the season and scoring against Derby for the fourth time.

The finish was his first since January when he struck in a 2-0 win over County at Elland Road. Patrick Bamford is back from a two-game ban on Wednesday but likely to begin the tie on the bench.

“Kemar made a lot of effort,” Bielsa said. “He moved all the time and he scored a goal, which is important for a number nine. All these are positives.

“Jack's pass was very good and it was decisive in this game. He had a good performance.”

Leeds entered the play-offs on a run of three defeats in four games but put a costly loss of form aside to strengthen their chances of promotion a few weeks on from allowing an automatic place to slip.

“It was painful for us not to be automatically promoted,” Bielsa said. “But we took the play-offs as a very important opportunity and I think we should value the opportunity of having a new possibility.”