The 31-year-old has failed to play his way into Unai Emery's good books since the ex-Arsenal boss arrived at Villa Park, although injuries have done him no favours.
Coutinho came off the bench for the final three minutes of the Lions' opening 5-1 loss to Newcastle United, before also enjoying a second-half cameo in a 4-0 win over Everton.
However, the Brazil international missed subsequent meetings with Burnley and Liverpool due to a hamstring injury - the severity of which was initially downplayed by Emery.
The Villa boss expressed optimism that Coutinho would return following the international break, and the English transfer window slammed shut with the attacker still on the books in the West Midlands.
A transfer to the Middle East was expected to materialise, though, as Coutinho found himself below John McGinn, Moussa Diaby, Leon Bailey and Roma loanee Nicolo Zaniolo in the pecking order.
Emiliano Buendia - who is currently out with an ACL injury - has also been preferred in the final third when fully fit, and Coutinho will now spend the rest of the campaign in Qatar.
Al-Duhail - who are managed by former Argentina striker Hernan Crespo - have acquired Coutinho's services on loan for the 2023-24 season, although it is not stated whether the deal also includes an option or obligation for a permanent move.
Coutinho joins a handful of recognisable names at Al-Duhail, including former Southampton midfielder Ibrahima Diallo and five-cap Portugal defender Ruben Semedo.
The ex-Liverpool winger was apparently wanted by Al Ettifaq head coach Steven Gerrard, who shared a dressing room with Coutinho at Liverpool before bringing him to Villa Park from Barcelona.
A reunion did not materialise, though, as Al Ettifaq brought in another two former Liverpool players in Jordan Henderson and Georginio Wijnaldum, and Coutinho's Villa deal still has just under three years left to run.
The Lions offered Coutinho an escape route from Barcelona in January 2022, and after coming up with five goals and three assists in 19 Premier League games, his stay was made permanent for €20m (£17.2m) that same summer.
However, the South American only managed one goal in 22 matches across all tournaments during the 2022-23 campaign, netting against Arsenal in a 4-2 loss to the Gunners at Villa Park.
Coutinho also missed out on a place in Brazil's 2022 World Cup squad due to a quadriceps injury, and the winger has not represented his nation since June of last year.
Coutinho follows Morgan Sanson and Viljami Sinisalo out on loan, while Villa have let Jed Steer, Wesley, Marvelous Nakamba, Jaden Philogene, Cameron Archer, Keinan Davis and Ashley Young leave the club permanently this summer.