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Jose Mourinho did it last night, as he brought Nemanja Matic back into his team for the Capital One Cup Cup showdown with Liverpool.
Matic, the Serbian strongman whom he calls "the giant," the man who has become such a key part of Chelsea this season. They had lost only once in 31 games with him in the team last season.
And facing him was another player just as important to Liverpool, in that same holding midfield position - Lucas. The man who ruptured his cruciate ligaments in a league cup quarter final at Stamford Bridge in 2011/12.
Liverpool skipper Steven Gerrard texted him as he was on the way to the final at Wembley, where Liverpool beat Cardiff on penalties, saying "Don't worry we'll be back." This was Lucas's chance. But the battle between the two midfield shields would be a crucial factor.
Since Lucas was restored to Brendan Rodgers' team, Liverpool, before last night, had lost just once in their last 16 games. That was game he was dropped for, at Manchester United.
Safety, security, reliability. And there it was in only the fourth minute as Lucas's superb tackle stopped Willian as he looked ready to slam home Diego Costa's pass.
And there was Matic, mopping up and clearing up as Liverpool, who started well last night, once again broke dangerously down Chelsea's right behind Branislav Ivanovic.
Lucas, meanwhile, was having a row with Jose Mourinho on the touchline after Costa stamped on Emre Can's ankle.
Once again Matic was covering as this time Can burst down the right, shepherding the ball to safety right on his goalline. The Serb's sheer appetite for hard work has made him a natural Mourinho player.
Liverpool though were giving him little room to move forward and be creative, Gerrard and Henderson nipping at his heels as soon as he got the ball. Though he did manage one snap shot just wide - and who was forcing to rush? Lucas, hustling as ever.
Lucas got lucky when his first error, a risky tackle on Oscar on the edge of the area reckless foul resulted in a free kick - but the Brazilian put it wide.
It was frenetic, as Matic lost his midfield partner Cesc Fabregas through injury. But the Serb and his rival were keeping things tight.
Lucas was booked as he stopped Oscar after Mamadou Sakho's error had left his team open, but had he not made the tackle Liverpool were in deep trouble.
As the teams began to tire, gaps began to appear. Still Matic surged forward, Lucas, the more conservative, held his position.
The Serb now had the more speedy, attack minded Ramires alongside him. It was still a battle of wills, a contest of speed of thought and deed in the middle of the pitch.
Time and again the pair clashed, intercepted, covered, chased. Matic, with Chelsea as the game wore on the more attack-minded, made more of his spindly, twisting runs. But always there was Lucas, chasing, blocking, making sure. Deadlock.
But then Lucas, in extra time, made one bad tackle too many. He felled Hazard on the edge of the area -Mourinho on the touchline was screaming at fourth official Phil Dowd that there should have been a second yellow.
The punishment was in fact worse. Willian swung in the free-kick and Branislav Ivanovic climbed to thump home his header.
For once, reliability had failed.