As Brighton & Hove Albion started the better team in this Premier League fixture on a sunny but brisk afternoon at Amex Stadium, Luis Diaz lost the ball in a strong tackle before Tariq Lamptey and Solly March scampered off to attack Liverpool's left flank.
The challenge happened right in front of Jurgen Klopp but rather than berate referee Mike Dean -- questioning the officiating would come later, once his side had secured a 2-0 win -- the Liverpool boss focused instead on a mild rebuke of Diaz, urging him to show more fight and chase after the Brighton duo.
Diaz heeded that advice and then some; less than 10 minutes later, he showed tremendous bravery to burst through Brighton's defence and meet Joel Matip's superbly lofted through-ball with a sharp header milliseconds before being poleaxed by Brighton goalkeeper Robert Sanchez.
As the 25-year-old lay stricken on the turf, VAR checked the collision but the red card for Sanchez many expected did not materalise. He wasn't even booked; it was a challenge which set Klopp off after the game down a familiar path describing the phrase "clear and obvious" as a "real problem" and a "good example of the issues we have" in determining when VAR intervenes.
"Everybody asked me today -- I didn't start the conversation -- about if it is a red card or not and if you get these situations you know most people think it was a red card," he said, before asking: "If everybody thinks it was a red card, for what reason could it not be a red card?"
Diaz will arguably not get a better example of English football's physicality, something it is traditionally said takes several months, or even longer, for overseas players to adapt to. Yet Diaz, a £37.5 million January signing from FC Porto, was thrown in at the deep end immediately. With Mohamed Salah and Sadio Mane engaged at the Africa Cup of Nations, the Colombia international was not afforded a slow introduction to help him acclimatise.
Saturday's outing on the south coast was Diaz's 10th appearance in the six weeks since Liverpool swooped in to sign him just as Tottenham believed they were finalising a transfer with Porto. Klopp had earmarked Diaz as a summer signing but the club were forced into moving swiftly as Spurs held advanced talks, and it could yet prove a decisive moment in Liverpool season.
"He is a very good player, let me say it like this," Klopp said. "We don't have groups in our team but we have a few guys who speak Spanish and Portuguese. That helps Luis a lot, they take him under their wing. He is in general a really nice kid.
"For the player, we just can say when we were looking at him ... it is not too easy to bring in a player in the winter without any kind of preseason but Luis was interesting because the way he played at Porto is exactly the way we wanted him to play here. He still has to adapt, especially defensively. But he can carry the ball pretty quick, his dribbling is not bad. I don't think we've seen already his full range of shooting skills. There is a lot of space for improvement but he is a good player."
Diaz has now started five of Liverpool's six league matches since joining the club, settling remarkably quickly into Klopp's attacking triumvirate, as much for his willingness to work off the ball as his potency on it. Since making his league debut on Feb. 10, Diaz is joint-fifth for shots at goal (19), sixth for shots on target (6) and joint-10th for chances created (11).
Diaz's form is also helping to mask a slight but perceptible dip in Salah's clinical touch. The Egyptian scored his 20th league goal of the season -- Liverpool's 2,000th in the Premier League -- with a 61st-minute penalty that settled the match as a contest after Yves Bissouma handled Naby Keita's shot. Yet this was an occasion where Salah's lasting impression centred on the chances he missed rather than the spot-kick he converted.
The 29-year-old has rightly forced his way into the conversation as to who is currently the best player in the world, but that status comes with heightened scrutiny of any profligacy in front of goal, any drop in the remarkable standards he has set.
After firing over from the edge of the box on the half-hour mark and being denied a trademark goal following a jinking run with a smart Sanchez save just before half-time, Salah went closer still after the restart. Cleverly working space for a shot in the box, his 57th-minute effort deflected off Brighton defender Lewis Dunk and struck the crossbar before he missed the best opportunity of all barely 60 seconds later. Diaz surged forward on the left and cut the ball back brilliantly into Salah's path, arriving with time and space to plant a shot on his favoured left foot. He could only drag the ball wide.
These can only be considered minor criticisms, given how Salah continues to threaten with sustained regularity and Liverpool remain on track in their pursuit of an unprecedented quadruple. But it is particularly timely -- if not remotely planned -- that Diaz has breathed fresh life into their multifronted challenge, perhaps even providing a little cover to the ongoing delay in Salah committing his future to the club with Klopp admitting this week that Liverpool "cannot do much more" in negotiations with his representatives.
Salah limped off with 25 minutes remaining here and Klopp explained afterward he had "overstretched his foot" but "thinks he'll be fine" with Arsenal next up on Wednesday.
The thought of Salah being absent for any period of time would have sparked panic for Liverpool. Diaz has some way to go to reach Salah's level, but his mere presence these days is bolstering Klopp's side no end.