Arsenal goalkeeper Petr Cech has hit out at Bayer Leverkusen after the Bundesliga club's Twitter account mocked his performance in Sunday's defeat to Manchester City.
With new Gunners head coach Unai Emery encouraging his team to play out from the back, Cech looked uncomfortable on occasion when trying short passes to his team-mates.
Cech was preferred in goal to summer arrival Bernd Leno, who joined from Leverkusen for a reported fee of £19.2million.
A video of Cech almost scoring an own goal as he attempted a pass across the face of his own goal started circulating on Twitter - with Leverkusen's English account getting involved.
"We might know a guy..." they replied to one Tweet highlighting Cech's error, seemingly suggesting their former number one Leno would be more adept at implementing Emery's vision.
We might know a guy...— Bayer 04 Leverkusen (@bayer04_en) August 12, 2018
That was followed by a 29-second video of Leno playing out from the back in a game for the German side, with the caption: "In case you were all wondering how to play out from the back..."
Retweeted over 1,750 times, plenty of supporters of both clubs found the reply humorous, but Cech took to Twitter to post a reply on Monday evening, criticising the "professionalism" of the post.
"@Arsenal we share important values which make us a big club not only on the football side . Fair competition, professionalism and sportsmanship are the biggest ones you teach young footballers and it's sad to see when other clubs don't share the same values. .@bayer04--en ," he wrote.
.@Arsenal we share important values which make us a big club not only on the football side . Fair competition, professionalism and sportsmanship are the biggest ones you teach young footballers and it’s sad to see when other clubs don’t share the same values. .@bayer04_en— Petr Cech (@PetrCech) August 13, 2018
Cech spoke after the game, in which Raheem Sterling and Bernardo Silva struck in each half as reigning Premier League champions Manchester City ruined Emery's welcome party.
The 36-year-old urged fans to give the team time to adapt to the new approach and said he feels adept at helping the team to build attacks from the back.
Asked by Press Association Sport if he is comfortable playing out from the back, Cech replied: "Yes, you play the best way for the team.
"I think that in a way if you want to dominate the game through possession you need to use every player.
"You can see at this level that one-v-one is difficult to play so you need to use the goalkeeper as a spare man every time you can - that is the role of the goalkeeper.
"If you play for a team who is happy to play a long-ball and a completely different way then the keeper plays a different way - but for what we want to do I think it is going to be important."
It remains to be seen whether Cech, who was named captain against City, will retain his place in goal when Arsenal visit his former club Chelsea on Saturday or if Leno will be handed his competitive debut.
Leverkusen's account replied to Cech's tweet soon after - saying their original "joke" had been taken more personally than it should have been.
It read: "Hi Petr. It seems our joke about wanting to see Leno, our former player, in action has been taken a bit more harshly/personally than intended. It was only a bit of banter. We're all for the values you've stated and wish you and your big club all the best. Nice 1v1 save on Aguero!"
Hi Petr. It seems our joke about wanting to see Leno, our former player, in action has been taken a bit more harshly/personally than intended. It was only a bit of banter. We’re all for the values you’ve stated and wish you and your big club all the best. Nice 1v1 save on Aguero!— Bayer 04 Leverkusen (@bayer04_en) August 13, 2018