The Manchester City midfielder, who cited international ambition as one of the principal reasons for rejecting the club's contract offer last month, was dismissed for two dangerous lunges on the Scandinavian pairing of Daniel Agger and Sami Hyypia as Liverpool moved to joint second in the Premiership with a deserved victory at Anfield.
The main concern for the watching Eriksson ahead of Wednesday night's friendly against Uruguay at the same venue will not be Barton's latest indiscretion, however, but the fitness of a player who dominated the midfield despite falling below his usual standards, and whose fitness remains essential to the aspirations of both club and country.
"His injury is not serious," said Rafael Benitez of the ankle problem suffered late on by Steven Gerrard. "And while I wouldn't tell Eriksson what to do, I think playing 90 minutes every week after 46 games this season is not ideal for the player." Not that Gerrard is often afforded a break by a Liverpool team who, as events in Benfica last week proved, cannot afford to grant him one.
Liverpool were comfortably superior and yet, with memories of conceding late against 10-man Birmingham still fresh, Anfield was consumed by tension in the closing minutes of this contest.
Such was the lack of creative endeavour from City that Barton's second booking in the 52nd minute appeared to seal their fate but, as is often the case, the 10 men rallied. Shortly afterwards, Jose Reina made his first save of the game from Bradley Wright-Phillips and then foiled Trevor Sinclair with an outstanding stop to turn his dipping volley away from the top corner.
The finest chance of an encouraging response then fell to Georgios Samaras, who was sent clear by Kiki Musampa of a ponderous Liverpool defence that sorely missed the suspended Jamie Carragher but sliced horribly wide as he closed in on goal.
That seven-minute spell aside, City did not perform yesterday and they missed the pace of Darius Vassell who missed out having been rested with a hernia problem. "Maybe we let go of our nervousness with 10 men because we had nothing to lose," pondered the City manager Stuart Pearce. "But until then we had shown Liverpool too much respect and over 90 minutes we didn't have a good go at them."
Pearce also sensed a nervousness about Liverpool "after about 35 minutes", although that was only on account of the home side's latest difficulty in establishing a lead.
Benitez's team had shown the attitude if not the quality required to enliven the game initially, as careless distribution and miscommunication between players irritated the Anfield crowd. City backed off and their supporters chanted for the introduction of Wright-Phillips long before the break. They fell silent in the 40th minute, however, when a combination of Gerrard's lofted pass and a wrong-footed Danny Mills gave Harry Kewell a free run at David James, and he converted low beyond the City goalkeeper.
Given their solid opening it was a simple goal for the visiting defence to concede and though Mills partially atoned by clearing Peter Crouch's header off the line on the stroke of half-time, it was the industrious Liverpool centre-forward who prospered thereafter. While this was the day the Kop's patience with Fernando Morientes finally snapped - the Spaniard's every error met with howls of derision - Crouch will have impressed. The England international was inches from converting Kewell's cross with a backheel flick, he saw a 20-yard shot tipped on to the crossbar by James and cut inside Richard Dunne only to be foiled once more by the City goalkeeper in the 74th minute.
Sixty seconds later Benitez withdrew his most threatening outlet, and then had the temerity to bemoan Liverpool's failure to find a second goal. "I am not happy with the final score," the Anfield manager said. "The three points yes, the score, no. We need to start finding a second goal and finishing these games off because we control games but then we become nervous. When teams go down to 10 men against us it is always difficult, because they defend in a different way. We became nervous and they had chances, we were controlling the game better with 11 men than with 10."
Goal: Kewell (40) 1-0.
Liverpool (4-4-2): Reina; Finnan, Hyypia, Agger, Riise; Kromkamp, Gerrard, Alonso (Hamann, 31), Kewell (Traoré, 85); Crouch (Garcia, 75), Morientes. Substitutes not used: Dudek (gk), Cissé.
Manchester City (4-4-1-1): James; Mills, Dunne, Distin, Jordan; Sinclair (Ireland, 67), Barton, Musampa, Riera (Croft, 78); Sibierski (Wright-Phillips, 46); Samaras. Substitutes not used: Weaver (gk), Sommeil.
Referee: D Gallagher (Oxfordshire).
Booked: Manchester City Barton, Samaras.
Sent off: Barton.
Man of the match: Gerrard.