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Ramsdale made his league debut following a £32 million summer switch from Sheffield United, after which reports emerged in Germany suggesting Leno had reacted badly but had been told he would start the north London derby against Tottenham later this month.
"No, that's not true," Arteta said on Thursday afternoon ahead of Saturday's trip to Burnley. "He responded, you can be frustrated, but he was top with his team-mates in training with everything so that is not true.
"I don't know where they are coming from but they are ahead of me! I think I am the one who picks the team at the weekend and sometimes I read things that I haven't decided yet. They give me ideas at the most, but nothing else because I haven't made a decision for Saturday -- so imagine [if I had] for the north London derby.
"What we want to do is empower performance and ask them to train, behave and play the best possible way. How can I guarantee somebody something?
"It wouldn't make sense with what we are demanding them to do. So it is on a daily basis, what you did three months ago in football, it doesn't count. So is what you're going to do today and tomorrow, and that's it.
"Aaron has come here to try to make us better. We needed a result on that day and I decided to play him. That's all."
The disappointment of missing out on European football for the first time in 25 years became a reality for Arsenal this week as the Champions League and Europa League group stages began with Arteta watching on from home.
"It hurts a lot," he said. "In the last few days it was hurting to put the television on and see those teams in there and you don't see Arsenal there, it was painful.
"I don't want to be sitting with Arsenal out of those competitions. We have the focus and the trigger is that."
Meanwhile, Arteta confirmed Arsenal are in talks with Jack Wilshere over allowing the midfielder to train with the club -- but stopped short of suggesting a short-term contract could be a possibility.
Wilshere is a free agent after leaving Bournemouth last season and was recently training with Serie B side Como in Italy as he searches for a new club.
The 29-year-old came through the youth ranks at Arsenal before making 197 appearances and Arteta said: "We are in conversations with Jack to understand what he needs, what he is looking for.
"It's a person and a player who has a huge admiration around everybody, not just the players or fans, but all the staff around here and we are willing to help him as much as we possibly can.
"He knows that and that's the situation. Could he play again? I wouldn't take it that far.
"What I'm saying is that we are in conversations with him to understand what he needs and how we can help him and that's it."