Joey Barton seems certain to be shown the door by Newcastle United this summer, whatever division the club are playing in. The troubled midfielder has spent time in prison and received a handful of final warnings since arriving at St James' Park from Manchester City for £5.8m two years ago, but his sending-off at Anfield on Sunday almost certainly came as the final straw.

Ignoring Alan Shearer's exhortations to stay out of trouble, Barton instead marked his comeback from injury by being shown a straight red card for a reckless challenge on Xabi Alonso ­during Newcastle's 3–0 defeat at Liverpool. It is understood that, having specifically warned the 26-year-old immediately before kick-off against ­making similarly ill-advised tackles, Shearer refused to accept the player's post-match apology. The pair are said to have clashed verbally in the dressing room and it was reported last night that Barton has been told to stay away by the club for a fortnight.

Barton, playing his first game since fracturing a foot in January, will be suspended for Newcastle's final three games of the season at home to Middlesbrough and Fulham and away at Aston Villa. He will also be fined two weeks' wages – £128,000 – by the club. "I thought he could do something different," said Shearer yesterday. "But I didn't think he'd go on and get a red card. I'd asked him not to do that."

Although a suspended six-game ban imposed by the Football Association last September still hangs over his head in the wake of Barton's training-ground assault on his former City team-mate Ousmane Dabo in 2007, Newcastle have been advised that it will not be activated by the tackle on Alonso as it is thought the ­sending-off was almost certainly for ­serious foul play. It would take a dismissal for violent conduct to trigger that additional ban and the FA expects to confirm that this is not the case on receipt of the referee Phil Dowd's report tomorrow.

Mike Ashley, Newcastle's owner, tried to offload Barton when he was imprisoned for 77 days last summer as the result of an assault in Liverpool's city centre in December 2007. However, Kevin Keegan, the club's then manager, talked Ashley out of it, persuading him that Barton deserved a final chance. When Bolton made a bid for his services in January, Shearer's predecessor, Joe Kinnear, again dissuaded Ashley from selling while also fending off interest from Ports­mouth. Future suitors will not be similarly discouraged.

In the meantime, though, Newcastle's focus is on avoiding relegation. To do so they will almost certainly be required to beat their relegation rivals, Middlesbrough at home on Monday.

"If we don't win against Middlesbrough it will be extremely difficult to stay in the Premier League," said Jonás Gutiérrez, Newcastle's Argentinian winger. "It's a difficult situation we are now faced with, but we can turn it round with the two matches we have at home. We will have to perform like they are two cup finals. If we take six points it will be a different situation."

Although Gutiérrez understandably side-stepped the Barton issue – "We can't think about Joey now, we have to think about players who can play," he said – the winger conceded that Michael Owen was desperately disappointed to start the Liverpool game on the bench in arguably the most controversial decision of Shearer's Tyneside tenure.

Like Barton, Owen will almost ­certainly be leaving Newcastle in the summer, but Shearer is expected to restore the ­erstwhile England striker to a three-man attack against Middlesbrough. "Michael wanted to play," said Gutiérrez. "He wanted to start rather than be on the bench but the manager is the manager and he decides who is in the team. But there is no doubt in my mind that Michael will be right for next week."