Mateusz Klich has come in for some big words of praise from head coach Marcelo Bielsa in recent weeks and showed why with a powerhouse performance and the winning goal in Leeds United's 1-0 win at Middlesbrough.
The victory was more comfortable than the winning margin would have you believe, but Klich's contribution proved crucial as he scored the only goal in first half injury-time.
It could yet prove important in the promotion race as it was enough to ensure Leeds stayed five points ahead of third-placed Fulham and six points in front of Nottingham Forest in fourth.
A third successive clean sheet brought a third successive 1-0 victory for Bielsa's men and they were good value for the success although the crossbar did come to their rescue when Marcus Tavernier's shot was inches away from an equaliser midway through the second half.
But Middlesbrough were only still in the game at this stage following yet more misses in front of goal by a United side that has still not solved its problems with finishing their good build-up play.
Leeds took time to get their game together after Boro's early pressing game made it difficult. But they should have been ahead in the 13th minute when the first chance of the night saw Patrick Bamford free in the area to meet Luke Ayling's chip in only for his header to lack power to be saved by home keeper Aynsley Pears.
Bamford, up against his former team, next met a low cross by Jack Harrison, but sent his instantly hit shot just wide.
Middlesbrough created their first opportunity on a quick break when Ashley Fletcher teed up Lewis Wing, but his shot from inside the area went wide.
Tavernier hit a long range shot well wide before Leeds were back on the attack soon after with Stuart Dallas playing a one-two with Pablo Hernandez and getting a good low shot in that was equally well saved by Pears.
Big appeals for a penalty fell on deaf ears when Helder Costa went down under a challenge from Adam Clayton and within two minutes United had two more efforts, Harrison's cross-shot being touched wide by Pears and Bamford's angled shot beaten away by the keeper.
Fletcher shot wide in a crowded area after a Boro free-kick was not cleared, but Leeds put a big finish into the first half to go ahead.
Initially it looked as if their frustrations were continuing when Hernandez hit the post with a shot after being set up by Bamford. But when the ball was not cleared Klich played a one-two with Hernandez and found the net via the post with a crisp low shot.
A lively start to the second half saw Dalls and Hernandez shots saved by Pears and Leeds keeper Kiko Casilla called into action to tip over a well struck long range George Saville strike.
Another appeal for a penalty was turned down by a referee who seemed reluctant to make decisions all night when Harrison went flying in the area after running into the box.
It was out of the blue when the hosts created their best chance as Tavernier found space in the area only to see his chip bounce to safety off the woodwork.
Two minutes later Bamford somehow failed to make enough of a decisive touch from no more than three yards out with the goal gaping after Luke Ayling's low pull back took a flick of Ryan Shotton.
In the last 10 minutes United seemed to settle for playing the game out, although they had another chance as Harrison went on a strong run only to shoot wide from inside the area.
Boro paid for their earlier exertions as they visibly tired, although they had one last opportunity as Tavernier's deflected shot was saved by Casilla after Wing's free-kick had been blocked, possibly by the arm of Dallas.
In added time Bamford fired over from a tough angle after working a short corner well, but it did not matter as Leeds comfortably saw out time for another important three points.
United boss Bielsa was pleased with aspects of his side's display.
He said: "The team fought a lot, very aggressive.
"The team made a lot of effort. When necessary the whole team defended. We attacked well, better in the first half than the second, with more chances.
"The team protected the result a lot. We played well in different moments of the match. The team didn’t lose their calm. In general, we managed well the different situations in the match.
"We had three times as many chances as them.
"The match was very tough, a lot of fight in the match. I think Middlesbrough was above their level in previous matches."
Leeds United 1
Middlesbrough: Pears; Howson, Moukoudi, Shotton, Friend (Johnson 63); Saville (Nmecha 67), Clayton; Tavernier, Wing, Coulson; Fletcher (Assombalonga 72)
Leeds: Casilla; Ayling, Berardi, Cooper, Dallas; White; Costa, Klich, Hernandez (Shackleton 73), Harrison; Bamford.
Referee: Gavin Ward