Arteta has urged his Arsenal players to take the club to a "different dimension" this season, declaring that success is now the standard, as the club also moved to clarify that Timber's return to London from training camp was a planned part of his injury rehabilitation rather than a fresh setback.
Timber missed two months towards the end of last season with an ankle injury before returning in time for the Champions League final defeat to Paris Saint-Germain, only for a groin issue to then rule him out of the World Cup.
The Netherlands international, who made 30 Premier League appearances as Arsenal won the title last season, has now travelled back from the club's training camp in Spain, but sources insist the trip is part of a scheduled rehabilitation programme rather than any indication of a relapse, with Timber expected to rejoin the squad in Spain shortly.
Arteta, meanwhile, used a message to the Arsenal App to set the tone for the season ahead following the club's first title in 22 years.
"This has to be the start and this has to be the standard," he said. "Excellence has to be our standard and this has to drive us to attack the future. The way we behave daily with more and more determination and ambition because we've shown that we've got it.
"Now we have to show that we belong to this level and we want to increase and take this football club to a different dimension."
Arsenal will go into the new season as favourites to retain the Premier League title and will also be targeting Champions League success after last season's penalty shootout defeat by PSG in the final, a result that prompted Arteta's calls for greater ambition in the transfer market.
That ambition has manifested in the club's pursuit of both Vinícius Júnior, who is yet to agree a new contract with Real Madrid, and Newcastle captain Bruno Guimarães, as Arteta looks to strengthen his squad in key areas.
"We all know about the context of this transfer window," he said. "From ownership to the board, the sporting director and myself, we know that we want to take this club to a different level. That is going to require a better squad, better individuals.
"We have identified where we have opportunities to grow and to improve and to evolve our game and what is going to be needed to achieve that. Hopefully very soon we can start to put things in a very concrete way."