Leeds United striker Patrick Bamford.

Bamford will make an unplanned start against Derby County on Wednesday, fresh from a controversial two-match ban, after Roofe was sidelined on the back of Saturday’s 1-0 victory at Pride Park.

Roofe claimed the only goal of the first leg to give Leeds a valuable advantage and leave the club within 90 minutes of the Championship play-off final but a calf strain will force him to watch from the stands on a crucial night at Elland Road.

The striker’s finish against Derby was his 15th of the season and his display showed renewed signs of the effective form he maintained prior to suffering a knee ligament injury in February.

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Bamford was missing at Pride Park as he served the second game of a suspension imposed on him for simulation during a clash with Anwar El Ghazi in last month’s 1-1 draw between Leeds and Aston Villa.

Cooper revealed that the forward had apologised to United’s squad for deceiving referee Stuart Atwell into sending off El Ghazi, incurring a misconduct charge from the Football Association in the process.

United’s captain, however, said “weird” confidence levels in Bamford would help the Chelsea trainee step into the gap left by Roofe and inspire the club through the second leg.

“He came straight in and apologised to me and the boys for what happened, and the staff,” Cooper said.

“It’s one of them things. In the heat of the moment sometimes you make stupid decisions and Pat will admit that but he’ll tell you that in these last 10 days when he’s been suspended, he’s certainly trained a lot harder than he would if he was playing

“There are no worries about Pat being fit and we all know what Pat can do . He’s got this unbelievable confidence about him where if he misses chances he always knows he’s going to score. It’s a weird confidence but a good one to have in the team. We all take from that as well.”

Roofe was Marcelo Bielsa’s first-choice forward up until his knee injury in February and has consistently looked more suited to United’s tactics under the Argentinian.

His movement troubled Derby on Saturday and his 55th-minute finish - a close-range shot at the end of a sublime cross from Jack Harrison - was his fourth against Frank Lampard’s side this season.

The forward joins Adam Forshaw, Tyler Roberts, Barry Douglas and Gjanni Alioski on the absentee list for Wednesday’s tie. Pontus Jansson is due to train tomorrow having sat out of Saturday’s first leg with an ankle problem.

Bielsa said: “It's always important to have players at your disposal who've played during the season. We always think of our squad as having 18 starters. It's not just a sentence, it’s the reality demanded by the competition.

“Of course we would like to have Roofe and Bamford with us and in parts of the season both were unavailable but the absence of Roofe comes with the availability of Bamford again.”

Leeds, nonetheless, have a significant initiative with a one-goal lead and home advantage in the return leg.

Lampard conceded that his team were outplayed again on Saturday, the third time that Derby have come off second best against Bielsa’s Leeds.

But Cooper said: “I don’t like to ever be over-confident. As soon as you start being like that it can affect the way you perform and your mentality.