Arca's future has been uncertain since his contract expired on July 1, but he has agreed to take a pay cut of more than 50 per cent to stay at the Riverside Stadium.
And that announcement was followed hours later by the news that top prospect Richie Smallwood has become the latest of the club's young guns to commit to a new contract.
Arca, 30, thought his time on Teesside was over ten days ago, when he left the training ground with his belongings disappointed that there would be no new contract agreed.
However, following further extensive discussions last weekend and more this week, Arca and Boro were finally able to come to an agreement over an outstanding payment the player felt he was due from his previous deal.
Mowbray seriously considered trying to lure PSV Eindhoven's Orlando Engelaar to the North-East, but in the end it has mattered little because his desire to keep Arca has come to fruition.
"It's fantastic news," said Mowbray. "Julio was outstanding last season and I'm delighted he has decided to extend his career at Boro.
"He is popular with the fans and in the dressing room and he is a player I value for the skill and experience he can bring to our team."
Arca, voted supporters' play of the year last season, will now be thrust straight into contention for this afternoon's trip to Leeds United.
But a deal for Belgium international Faris Haroun has not been completed in time for him to play at Elland Road. There are not believed to be any significant problems and the Germinal Beerschot midfielder is likely to sign early next week.
And while he is waiting to see if Swansea City step up their interest in Matthew Bates, whose sale would boost his spending arm, Mowbray is happy to have secured the services of Smallwood until the summer of 2014.
And Smallwood, 20, said: "All I ever wanted to do is play for this football club and I'm glad we have been able to sort all the details out quickly."
Having previously got Marvin Emnes, Joe Bennett, Jason Steele, Seb Hines, Luke Williams, Cameron Park and Connor Ripley tied down to lengthy deals, there will now be a drive over the coming weeks to agree new contracts with other members of the squad.
Mowbray, who did not want to discuss names, said: "Since we've come in, the ones we've identified that we liked, we try to give them longer contracts and there's one or two others over the next few weeks you will hear are signing extended contracts.
"We're just trying to put a nucleus of players together that might be here for the next three or four years, we're not interested in speculation on who wants to buy them."
With Marvin Emnes, Scott McDonald and Lee Miler the only recognised senior strikers in the squad, Boro are an injury away from a striker problem, particularly with Merouane Zemmama out until September with a hip complaint.
Former Chelsea striker Mikael Forssell has been linked in recent days, while Mowbray has already missed out on Ishmael Miller.
"We're very short on strikers but again it revolves around money, so if there's a sale we'll be looking to spend some of that money," said Mowbray. "I think we'd like another few for the days when injuries and suspensions come along so we are not having to rely on the young boys. A striker is the priority now."
Mowbray was a Boro fan in the days when the derbies with Leeds were much more than they are now. Even in the modern era, though, there is a bite when the two clubs meet.
"Leeds-Middlesbrough is always a big game, I remember growing up as a boy travelling to Elland Road to watch the games and they were always feisty," said Mowbray, keen to build on a start that has seen Middlesbrough draw with Portsmouth and defeat Walsall in the Carling Cup.
"Leeds won't be happy with their result on the opening day at Southampton and they are without a few strikers.
"We have to see if we can put them on the back foot."
Source: Northern Echo
Source: Northern Echo