NEWCASTLE 2 MAN CITY 1 (Rondon, Ritchie (p))
Dubravka, Yedlin, Schär, Lascelles, Lejeune, Ritchie, Pérez (Manquillo 90+1), Hayden, Longstaff, Atsu (Kenedy 87), Rondón
Subs: Clark, Murphy, Fernandez, Roberts, Woodman
Rafa always insists survival in the league means more than cup success.
Personally, I'd rather see Newcastle win the FA Cup and be relegated, but many beg to differ.
And Rafa's tactics worked well for him as United produced the shock of the night, and how Liverpool supporters must be thanking their lucky stars.
Matt Ritchie fired Newcastle to a first Premier League victory over Manchester City in 23 attempts as the champions' hopes of retaining their title suffered a major blow.
Ritchie's 80th-minute penalty completed a remarkable turn-around as the Magpies, who had fallen behind to Sergio Aguero's strike just 25 seconds into the game, produced the most unlikely of fightbacks.
The 2-1 defeat wrecked City boss Guardiola's hopes of marking his 100 Premier League game with a record 74th victory and left Liverpool four points clear at the top of the table ahead of Wednesday night's home clash with Leicester.
Salomon Rondon had cancelled out Aguero's strike with a 66th-minute equaliser, but on a night when some of the edge had been taken off a mutinous atmosphere by the news that Miguel Almiron was on his way to Tyneside to complete a move from Atlanta United, Rafael Benitez's men produced a performance of real character.
That outcome looked unlikely when David Silva slipped as he attempted to reach Raheem Sterling's cross and collided with keeper Martin Dubravka, who was still on the ground as Aguero hooked home the lose ball.
Kevin De Bruyne had barely reached the bench by the time the Magpies dragged themselves back into the game, Rondon reacting most effectively after Isaac Hayden had helped the ball into the penalty area to volley past Ederson.
And it got worse for the visitors with 10 minutes remaining when Fernandinho toppled Sean Longstaff inside the penalty area and Ritchie stepped up to smash the resulting penalty past Ederson.
Manchester City's title hopes suffered a huge blow as Newcastle came from a goal down to record a remarkable victory over the defending champions at St James' Park.
Two defensive lapses cost Pep Guardiola's side the chance to cut Liverpool's lead at the top of the Premier League to one point. The Reds face Leicester at home on Wednesday.
City could not have got off to a better start when Sergio Aguero hooked home after only 24 seconds.
The Argentine also had a goal disallowed soon after when referee Paul Tierney adjudged Kevin De Bruyne had delivered a free-kick before he gave him the signal. The Belgian was booked as a consequence.
Guardiola's side rarely troubled Magpies keeper Martin Dubravka thereafter, and Rafael Benitez's men grew in belief.
The home support erupted in the 66th minute when Salomon Rondon instinctively fired in after connecting with Isaac Hayden's header from 12 yards out.
And the match turned on its head in the 78th minute when the Magpies were awarded a penalty after Fernandinho - overplaying at the back - fouled Sean Longstaff in the area after being robbed of possession.
Pep Guardiola's City have dropped more points this season than they did in the entirety of the 2017-18 title-winning campaign
Many will be looking at this scoreline in disbelief.
City had not lost to Newcastle in 22 league games, with the North East club having only collected three points from a possible 66 against their opponents.
Guardiola's side came to St James' Park on the back on a 5-0 thrashing of Burnley in the FA Cup, and having put three goals past Huddersfield and Wolves in their previous two league encounters.
Nothing less than three points seemed likely and when Aguero fired City into the lead inside a minute, following a cross from Raheem Sterling, that became an apparent certainty.
But then City eased off the pedal.
They continued to dominate possession but Newcastle sat deep and only allowed City's widemen to get in behind them on a handful of occasions.
Sterling should have made the most of those rare crosses that got through into the six-yard area, but he failed to attack Leroy Sane's delivery - much to the frustration of his manager.
And Magpies keeper Dubravka only made one save of note - a block to keep out David Silva's effort in the 58th minute, which was City's final effort on target.
This defeat could be the moment City look back on as pivotal in the title race.
Are dark clouds starting to shift over Tyneside?