The 24-year-old rose to prominence in his homeland and was supposedly targeted by Manchester United before joining Mikel Arteta's side in a deal worth £29.6m.
Vieira arrived in North London on the back of registering an unparalleled 14 assists in the 2021-22 Primeira Liga season, and he hit the ground running at Arsenal with a fine strike in a 3-0 win over Brentford.
The former Portugal Under-21 international also scored the winning penalty in last year's Community Shield win over Manchester City, but he has failed to make a consistent impression in an Arsenal shirt.
Often playing second fiddle to both Martin Odegaard in the number 10 role and Bukayo Saka on the right wing, Vieira has registered just three goals and nine assists in 49 Arsenal matches, although he was not helped by a serious groin injury last season.
Vieira 'to rejoin Porto' as Arsenal close in on Mikel Merino
The 24-year-old played a prominent role in pre-season, scoring in a 1-1 draw with Bournemouth in the United States, but a hip problem prevented him from making the squad for last weekend's Premier League opener with Wolverhampton Wanderers.
Vieira was spotted in training on Friday ahead of the weekend's battle with Aston Villa, but according to The Athletic, he is now on the cusp of returning to Porto on a temporary deal and will not travel to Villa Park either.
The playmaker played 76 times for the Portuguese giants before heading to England, banking 10 goals and 18 assists, and he will be expected to enjoy regular game time with his erstwhile employers.
Vieira's move back to Porto is expected to be a straight loan without an option to buy, and he remains under contract with Arsenal until 2027, but what the future holds for him beyond 2025 is unclear.
In a separate update from Fabrizio Romano, the transfer expert claims that a deal for Vieira will be given the green light if Francisco Conceicao completes an expected move to Juventus.
Vieira exit to boost Ethan Nwaneri's first-team prospects?
Following claims from last season that Vieira was not impressing Arteta in training, it was always difficult to envisage the versatile attacker becoming an integral part of the Spaniard's plans in 2024-25.
Vieira's temporary exit leaves Saka significantly short of cover on the right wing, though, and the Englishman would have no recognised backup if Reiss Nelson also leaves before the August 30 cut-off point.
However, Arteta would surely not let both Vieira and Nelson leave without a well-thought-out plan, and unless the Gunners are secretly working on a new attacking signing, Ethan Nwaneri could be the answer.
The 17-year-old is being tipped to enjoy a breakthrough season in the Arsenal first team in 2024-25, and even though he has mainly played as a number 10 in the early stages of his career, he is no stranger to the right-wing position.
As a result, Nwaneri may act as Saka's deputy throughout the 2024-25 season, especially as the incoming Mikel Merino - who was pictured at a Spanish airport on Friday - will reinforce Arteta's central ranks