The striker signed an emergency loan deal in order to play against Burnley while Boro finalise a permanent move from Coventry, but it proved in vain as first-half goals from Jay Rodriguez and Kieran Trippier condemned the Teessiders to defeat at the Riverside.

"It was frustrating not to tie it up properly in time for him to play," admitted Mowbray.

"Everything is done and everything is agreed but we missed the deadline to register.

"So we asked the Football League about a loan move and they gave us the go-ahead.

"We needed him because on Friday we only had one fit striker. Scott McDonald has been ill but he pulled a shirt on today and played or there is every chance Lukas might have started today even though he hasn't trained with the team.

"Lukas gives an extra dimension up front. He is big and physical and strong and has qualities we didn't have in the squad and that means we can utilise a different approach if we need it.

"And we do at times. We know that. We huffed and puffed at times and we couldn't score a goal.

"That has been an issue for us for a while now but usually we have managed to nick one and win 1-0. We couldn't do that today and it was very frustrating. We are all disappointed."

Burnley boss Eddie Howe though was delighted with the polished win that kept his side moving up the table.

"We played very well," he said.

"We counter-attacked superbly in the first half and at times we cut them open. We could have had more goals if truth be told.

"But I am just as pleased with the second half because they came at us a bit more and when we were under a bit of pressure we worked very well to close the game out.

"We've won seven out of nine now. There's no reason if this squad can keep it up that we can't compete with the very best in this league."

Burnley had the upper hand from the start against an off-colour Boro and went close several times before they took the lead after five minutes from a well-worked corner routine.

Ross Wallace swung in the set-piece towards David Edgar who dummied it and let it roll through to Rodriguez on the penalty spot to lash home the opener.

Soon after they went close again as Junior Stanislas drilled a low ball across the face of goal for Rodriguez to come racing in at the far post and stretch to stab just wide.

Burnley got the second in the 28th minutes as a cross into the box was hooked clear by Joe Bennett but fell to Trippier 25 yards out and he fired in a cracking shot that skidded beyond the dive of debutant goalkeeper Connor Ripley and home.

Boro had a chance to pull one back just before the break as Justin Hoyte latched on to the ball after a scramble in the Burnley box and squared for McDonald unmarked at the far post, but the Australian missed the ball completely.

Boro had more possession in the second half but looked laboured and failed to find a way through a well-drilled Burnley defence.

Their best chance came a minute from the end as Hoyte found substitute Tony McMahon in the box but his close-range angled effort was well saved at the near post by goalkeeper Lee Grant.