Alen Boksic looks certain to miss Middlesbrough's biggest test of the season

after failing to recover from knee ligament damage.

Bryan Robson was hoping the Croatian would be back to lead what looks like

Mission Impossible against Manchester United tomorrow after being kept out

for four games by the injury.

Boksic would have lifted Boro's slim hopes of creating a major upset but he

failed to make it in a test yesterday and now looks booked for a seat in the

Old Trafford stand.

The 30-year-old has scored five goals for Boro but has started only six

games since a £2.5m move from Lazio, though Robson insists there are no

concerns about his fitness.

"We thought he would be back quicker but there was a slight

misunderstanding about the injury because of language difficulties," said

Robson.

"His record before he came here is good, he's only had one major injury in

his career and that's not bad for a striker of his age.

"It's true we were a bit anxious when he had problems at the start of the

season but not now. It's been very frustrating for him but I expect him back

next week."

And Robson is demanding his players copy the Manchester United example by

producing a high work-rate.

There has been criticism this has not been the case in certain games this

season, a worrying sign for any manager, and Robson said: "United have great

players but they work very hard in every game and that's what I have been

impressing on every player here.

"You have to do it consistently. When you do, anything can be achieved.

"If the players show the same committment as against Arsenal last week, we

can take something from Old Trafford." But Boro's record of five defeats in succession and a place in the bottom

three hardly inspires confidence when ranged against United's record in the

Premiership.

They have dropped two points out of 18 and conceded just three goals at

Old Trafford and lost just one league game all season.

Boro will also be without skipper Paul Ince plus Ugo Ehiogu, Keith O'Neill,

Robbie Mustoe and Paul Okon.

But first-choice Mark Schwarzer is scheduled to return, which will be a

relief to Robson after the costly errors by the stand-in 'keepers.