Cast in the role of the false nine, as his club arrived in London without a recognised striker due to the suspension to Luis Suárez and Fabio Borini's injury, Shelvey put in the hard yards, his commitment attempting to mask his lack of comfort as the leader of the line.
His reward was glorious. Shelvey might struggle to claim the winning goal, as the crucial touch appeared to come off the West Ham United defender James Collins, but he was the central figure from a Liverpool perspective when the substitute Jordan Henderson flashed in his 79th-minute cross.
Shelvey supported West Ham as a boy and his goalscoring team-mates, Glen Johnson and Joe Cole, began their careers at the East End club. They did not celebrate their goals, which were of the highest class, particularly Johnson's and, at full-time, Cole applauded the supporters in the home seats.
This was a game that lurched one way and then the other. For so long, it appeared that Steven Gerrard would, curiously, be the West Ham matchwinner. Jeered throughout by the home crowd – they cannot forget his heroics against their club at the 2006 FA Cup final – the Liverpool captain's rogue back header had given West Ham the advantage.
But Liverpool were composed in the second half and, gradually, took a grip on the game. Cole's equaliser would have been enough for the headline writers but Shelvey helped to trump him to secure a big victory for the manager Brendan Rodgers and the club.
Suárez's absence had overshadowed the build-up but Johnson seemed intent on filling the creative void, despite his status as a right-back. He pushed high up the field at the outset to worry Matt Jarvis, West Ham's covering winger, who was rather more comfortable in the attacking third, and his goal was the sort to draw the breath.
Johnson collected a raking Gerrard pass and glided inside, away from Jarvis. Once close to the edge of the area, he shifted the ball onto his right foot and, with Joey O'Brien failing to close him down, he unfurled a stunning drive into the far top corner. Out of respect to his first club, he did not celebrate.
Raheem Sterling missed a glorious chance for 2-0, after Johnson had beaten Jarvis to cross but West Ham fought their way back. Liverpool struggled to contain the rampaging Mohamed Diamé, who had gone close with an early shot that deflected wide off Carlton Cole, and both Sterling and Gerrard were booked for fouls on him. Diamé might have signed for Liverpool under Kenny Dalglish and it was a great shame that his afternoon would end prematurely.
He had taken a bang on the leg from Sterling and, moments later, on 73 minutes, he crumpled to the turf under no challenge. He departed on a stretcher.
Daniel Agger made a saving clearance ahead of Cole from Jarvis's cross but the game turned sharply on West Ham's penalty. Guy Demel's rasping shot struck Joe Allen's arm, as the Liverpool midfielder attempted to close him down. Allen was only yards away and the shot travelled at great velocity but his arm was out. Mark Noble showed no sympathy with a clinical low conversion from the spot.
Things got worse for Liverpool when Gerrard leapt and misdirected an attempted clearing header from another Jarvis cross. He was under no real pressure from but the ball looped beyond his own goalkeeper, Pepe Reina. The aberration carried shades of his own goal in the 2005 Carling Cup final defeat to Chelsea.
Rodgers had introduced Cole for the injured José Enrique on 28 minutes – the former West Ham favourite was afforded a rousing round of applause from the Upton Park crowd – and Liverpool probed patiently in the second-half.
Cole drifted inside from the left and the overlapping full-back Stewart Downing twice created chances. On the first occasion, Cole's dummy ushered in Sterling to test Jussi Jaaskelainen and on the second, Shelvey headed wide.
Liverpool were in charge and the equaliser had been advertised, even if the identity of the scorer had not. Cole last scored a Premier League goal in Liverpool's 5-0 drubbing of Birmingham City in April 2011 but his low left-footed shot, after Sterling had swapped passes with Shelvey and then teased him through, was made to measure inside the far post. Like Johnson, he kept his celebrations in check.
The winning goal was all about the power and presence of Shelvey, even if it appeared to loop home off Collins. Shelvey muscled his way in front of the defender to meet Henderson's low cross from the right and as he took in the acclaim of the travelling support, no one in Liverpool colours seemed to care who had contrived the decisive touch.