Just a few days ago, it was being discussed whether Liverpool could do the quadruple. Now the question is do they have the strength in depth to win on multiple fronts this season?
Arne Slot made 10 changes for the trip to Plymouth, confident enough to leave the likes of Mohamed Salah and Virgil van Dijk behind.
He would have wished he could have called upon his Egyptian king in the second half at Home Park, as Liverpool's fringe players laboured to break down the Championship's bottom club.
Salah has scored 60 per cent of Liverpool's Premier League goals this season - is this where they'd be without him?
Slot stood by his selection afterwards, highlighting both the need for his first team to get a breather during a relentless schedule and for their back-ups to get some much-needed game time.
But he also pointed out that many of these reserve players also had an opportunity in Liverpool's final Champions League game, when progress to the last 16 was assured - and that they had lost that one too.
Many of the young players fielded don't deserve individual criticism, such is their inexperience. But there were senior players on the pitch too who looked well short of the required level.
Federico Chiesa was one of them. A player who has had to wait for his turn but did nothing to show he was ready for big-match minutes. Darwin Nunez failed to fire off the bench, while Diogo Jota and Luis Diaz had little impact across the 90 minutes.
Expect the big names to return for Wednesday's Merseyside derby, when Liverpool can extend their Premier League lead to nine points. But if those star players are forced out during the run-in, how many of these players on show on Sunday can Slot trust to step in and deliver?
Peter Smith
Tottenham have injuries but so do Aston Villa.
Isn't top-level management about being able to fix problems that arise throughout the season? Adapt or die. Find a way.
Well, Tottenham and Ange Postecoglou don't adapt. The Spurs boss yet again pointed to his injury list in the aftermath of this defeat but the sympathy act is wearing a little thin now. Villa ended the match without a fit or available centre-back to pick from after Ezri Konsa joined their long list of absentees. Yet Unai Emery found a way to get his team playing his football and still protected their potential vulnerabilities at the centre of their defence. That's how to fix problems.
Tottenham are 14th in Premier League - 16 points behind fourth-placed Chelsea and are now out of both cup domestic cup competitions. The final three months of this season are going to be a slog for followers of this football team with nothing domestically to play for.
It truly is Europa League or bust for Tottenham's season now, with or without Postecoglou in the dugout.
Lewis Jones
Progressing into the fifth round is exciting enough but the cameo performances from new signings Marco Asensio and Marcus Rashford have left Aston Villa fans desperate to see more.
"This is probably the best squad we've ever had," Jacob Ramsey, who scored the first goal against Tottenham in the 2-1 win, told the BBC after the game.
"You see the bench with (Donyell) Malen starting and Rashford coming on. The squad depth is unbelievable.
"The starting players have to raise their game as the players coming on are a big threat."
Despite only spending a few training sessions with their new squad after signing in the final days of the January transfer window, Rashford and Asensio linked-up seamlessly with their team-mates and were unlucky to walk away without assists to their name.
Unai Emery now has an abundance of world-class talent at his disposal but the same problem he experienced with Jhon Duran prior to his move to Al Nassr now presents itself again: how can he use them all together?
However, in terms of problems in football, it is the best one to have.
Patrick Rowe
When Chelsea last met Brighton in late September, they scored four goals. Cole Palmer got them all. Crucially, they were in the run of being the Premier League's great entertainers.
Now the Blues' output appears to have frozen. This was the fifth time since Christmas where Chelsea have taken a lead and not seen the win through. Leads have been chucked away for dropped points against Fulham, Crystal Palace, Bournemouth, Manchester City and now Brighton.
After their last defeat against City, Gary Neville accused Chelsea of missing an opportunity at the Etihad and their FA Cup exit followed the same story.
They faced a Brighton side who shipped seven last weekend, saw their goalkeeper chuck one into his net after five minutes on Saturday and even captain Lewis Dunk came off at half-time to destabilise the Seagulls' backline even further. But Chelsea could muster just one shot on target - which came just four minutes in.
After scoring four in the last encounter between these two, Palmer was nullified. Christopher Nkunku's rustiness was clear to see - his 33 touches was the second-lowest tally out of Chelsea's starters. He also failed to have a shot all game.
Nicolas Jackson could come back for the next trip to Brighton on Valentine's Day but even he has gone eight games without a goal. How Chelsea get out of this rut of not scoring enough and throwing away leads is unclear at the moment.
Sam Blitz
Manchester City survived Leyton Orient's scare from the first half to progress into the fifth round - but it came at a cost.
Their £50m Deadline Day signing Nico Gonzalez - who was dubbed as Rodri's replacement as he continues his comeback from injury - lasted 22 minutes before limping off the pitch on his debut.
Prior to exiting the field with what looked like a hip or lower back injury, Nico was caught on the ball before Jamie Donley launched his shot from just inside the halfway line to give his side a shock lead.
A whirlwind debut for the 23-year-old, who has quickly learned what English football could have in-store for him.
"I think Nico understood immediately what the Premier League is and referees," Pep Guardiola said after the game. " I don't know how hard the shot was but he couldn't continue."
Patrick Rowe
Patrick Dorgu was the shining light in Manchester United's dire first-half performance against Leicester.
The £30m signing from Lecce made his debut at Old Trafford although was unexpectedly deployed at right wing-back while Diogo Dalot played on the left.
"He played a lot of time at Lecce on the right and the left," explained Amorim. "Sometimes you need a left foot on the right side to come inside and connect in a different way, and sometimes you need a right-footer to connect and cross more balls."
Dorgu linked up nicely with Amad Diallo on the right and raided forward, albeit he couldn't find a telling pass on one occasion when he got into the box.
"He was a little bit anxious in the first touch with the ball," added Amorim, who substituted Dorgu at half-time. "It's a different league for him, different speed of the game, but he did well."
David Richardson
It has been 70 years since Newcastle last lifted a major domestic trophy - they are on the right track to win two in one season.
Eddie Howe's side backed up reaching the Carabao Cup final on Wednesday night by coming through a tough test at League One leaders Birmingham City in the FA Cup fourth round.
Newcastle made nine changes yet their second-string side showed character after falling behind inside the opening 40 seconds and mettle to match the hosts' tough tackling in the second half.
The only blight on their evening was an injury to Dan Burn. "In the last couple of weeks, we seem to have picked up a couple. It would be the last thing [we need] to derail us," said Howe.
For a club that's waited 70 years for silverware, the next few months could be nothing short of historic.
David Richardson
Bournemouth made their win at Everton look routine and that's what should worry any potential opponents come Monday's draw.
Andoni Iraola has his side currently enjoying a run of 14 games without defeat after they overcame a rejuvenated Toffees side to book a spot in the fifth round of the FA Cup.
"You wouldn't want to get drawn at home to Bournemouth in the next round," Sky Sports pundit Paul Merson said on Soccer Saturday.
"They've made three changes this afternoon and were still outstanding.
The Cherries have never got beyond the quarter-final of the FA Cup but their current displays, led by the likes of Antoine Semenyo and Justin Kluivert, will be enough for Bournemouth fans to dream.
William Bitibiri
