Liverpool red shows inconsistencies, Manchester United's issues remain and Alexis Sanchez could turn Arsenal toxic

Seven things we learned this weekend: De Boer won the sack race as Spurs and Arsenal fightback

Sadio Mané's sending-off stole the headlines but Liverpool's response was more concerning (Getty)

The Premier League is back after the unwanted early-season international break, and as usual there are plenty of key talking points.

We have had our first managerial sacking of the season as Frank de Boer won the sack race at Crystal Palace, despite fierce competition from Slaven Bilic at West Ham.

Manchester City made a statement of intent with a 5-0 thrashing of Liverpool, albeit against 10 men, but the red card was the biggest issue to come out of the Etihad.

Manchester United lost their 100 per cent record to Stoke, but Tottenham and Arsenal both bounced back from rocky starts to the season with confidence-boosting wins against Everton and Bournemouth respectively.

Here are seven things we learned from the Premier League this weekend…

Mane red card but Ritchie yellow?

Sadio Mane’s dismissal dominated the weekend’s talking points with the incident looking little more than a late, accidental collision in real time – but a reckless and aggressive kick to the face when slowed down. With the injury suffered by Ederson, it can be seen as the correct decision by referee John Moss as it was indeed dangerous.

Sadio Mane was sent off in the first-half following this high boot on goalkeeper Ederson (AFP/Getty Images)

However, just 24 hours later the debate was magnified after Matt Ritchie was only shown a yellow card by referee Mike Jones for a raised boot which also made contact with the face, in this case belonging to Swansea’s Alfie Mawson. Mawson stayed on the pitch showing that it was the damage caused by Mane which set the two incidents apart, but the consistency of referees is against being called into question.

United still have the same issues

Three consecutive wins, scoring 10 and conceding zero in the process, may have disguised some of Manchester United’s more obvious issues which just aren’t going away. Their attack came unstuck against Stoke in the 2-2 draw, with Romelu Lukaku again showing he needs more than one bite of the cherry to score after missing a glorious late chance to snatch victory, just two weeks after missing a penalty against Leicester. He scores plenty, but so did Zlatan Ibrahimovic, who also missed a hatful of chances in games.

Romelu Lukaku has spurned a number of chances already (Getty)

However, one of the greater issues is at left-back which Daley Blind and Matteo Darmian have so far job-shared, with the latter becoming unstuck against Stoke. The Italian was consistently exposed, most notably for Stoke’s opener, by Mame Briam Diouf – a striker being played at right wing back. He did well to launch the attack for United’s second goal but Jose Mourinho will be hoping Luke Shaw can finally fulfil his potential on his return from injury. Striker and left-back problems... sound familiar?

Kane is back but can Spurs take away performance home?

August is over and Premier League defenders are once again fearing Harry Kane. He may not have ended his start-of-the-season curse but his two-goal performance, and 100^th top-flight strike, against Everton to kick off September has kicked Tottenham into life.

Harry Kane celebrates scoring his second for Tottenham (Getty)

However, can he, and Spurs, replicate it at Wembley? Mauricio Pochettino’s side have six points from two tricky away trips to Newcastle and Everton but have only taken one against Chelsea and Burnley at home so far. And, with two games at the national stadium in the coming week, against Borussia Dortmund and Swansea, Kane’s goals will be crucial in ending the Wembley woes.

Sanchez turns up Emirates toxicity

Alexis Sanchez has a lot to do to rediscover his adoration from the Arsenal fans after falling so far in their eyes over the summer. Not signing a new contract is disappointing, but to push to move to a fellow Premier League side, especially Manchester City who have poached so many of Arsenal’s top stars, left loyal Gooners fuming at the Emirates.

Sanchez was deemed not physically ready to start against Bournemouth (Getty)

Sanchez’s second-half introduction was greeted with a chorus of boos and while Arsene Wenger is confident the Chilean can win them over with his performances, the jeers will only get louder as January rolls over and he can negotiate with other clubs. The mood at the Emirates is already worrying but this could turn it toxic.

Swansea must build up Sanches

From Sanchez to Sanches – Renato Sanches. Since rejecting Manchester United to join Bayern Munich and subsequently winning young player of the tournament at Euro 2016 12 months ago, Sanches now finds himself battling in relegation-candidates Swansea’s midfield. With no disrespect to Swansea, that is quite the fall.

Renato Sanches made his eagerly-anticipated debut for Swansea (Getty)

But Swansea in many ways is the perfect club for him to get his career back on track. Playing week in, week out in high-pressure circumstances, Paul Clement can build the team around him, boosting his confidence and getting him feeling like a world-class player again. He looked devoid of that swagger on his debut against Newcastle on Sunday but if that returns this loan could work out expertly for both parties.

Palace move quickly

There were suggestions Frank de Boer could be the first managerial casualty following Crystal Palace’s last game, a 2-0 home defeat to Swansea, but the club kept him on for them to go on and secure an unwanted record of losing all four of their first four Premier League games.

Frank de Boer was sacked on Monday morning after a fourth defeat from four (Getty)

They now have sacked him after the loss to Burnley and, unless a new manager brings about new change, they face losing all eight of their first eight games. Next Palace face a Southampton team managed by someone who was among their first choices for De Boer’s job – Mauricio Pellegrino – with away trips to Old Trafford and the Etihad before champions Chelsea visit Selhurst Park. Zero points from eight is a tough place to come back from.

Morata head and shoulders above the rest

Alvaro Morata arrived in England as the £67m consolatory prize for missing out on Romelu Lukaku, but he may not come across that way by the end of the season. So far the Spaniard has three goals and two assists from his four games – and all with his head.

Being an established header of the ball is always a bonus in the Premier League and having signed a player who is considered the best crosser of a ball in Italy in Davide Zappacosta, don’t be surprised to see him add to those aerial stats. Diego Costa who, right?