Under-performing Gasly will go in the other direction, taking British-born Thai driver Albon’s seat at the sister team where the 23-year-old Frenchman started out before being promoted at the end of last year.
The Belgian Grand Prix at the Spa-Francorchamps circuit is on Sept. 1, the first race after Formula One’s August break.
“Red Bull are in the unique position of having four talented Formula One drivers under contract who can be rotated between Aston Martin Red Bull Racing and Toro Rosso,” Red Bull said in a statement.
“The team will use the next nine races to evaluate Alex’s performance in order to make an informed decision as to who will drive alongside Max in 2020.”
The switch-around marks a meteoric rise for Albon, who was racing in Formula Two last year and seemed destined for a future with Nissan in the all-electric Formula E series before Red Bull stepped in.
The energy drinks brand had dropped him from their young driver program in 2012 but he has seized the second chance they gave him.
Last month’s German Grand Prix at Hockenheim was Albon’s first wet F1 race and he now finds himself in a winning car after just 12 grand prix starts.
Being up against Verstappen will be a tough challenge, with the sport’s youngest ever race winner the on-form driver and seen as a champion-in-waiting.
The Dutch 21-year-old has won two of 12 races this season and is third overall on 181 points while Gasly, the 2016 GP2 (now F2) champion, has struggled with just 63 points.
To add to his embarrassment, the Frenchman has been twice lapped by Verstappen.
Honda-powered Red Bull are third in the constructors’ standings but need both drivers finishing consistently high up to have a chance of overtaking Ferrari, who are 44 points ahead of them in second place with champions Mercedes far in front.
Team principal Christian Horner expressed his frustration at the most recent race in Hungary in which Verstappen started on pole position and finished second to Mercedes’ Lewis Hamilton with Gasly only sixth.
“The start wasn’t great, the first lap wasn’t great and we shouldn’t be racing Saubers (the Alfa Romeo cars) and McLarens,” he said. “We need him to be racing Ferraris and Mercedes. The problem is he’s not in the mix at all.”
Gasly performed well last year at Toro Rosso and moved up to Red Bull when Australian Daniel Ricciardo decided to move to Renault.
His demotion means Toro Rosso now have two drivers rejected by Red Bull, with Russian Daniil Kvyat also promoted early in his career, then demoted and dropped entirely before being given a second chance.
“We’re excited to see Alex get the opportunity, and we’re happy to be working with @pierregasly again,” Toro Rosso said on Twitter.
Albon has got himself noticed this season with strong performances, singled out even in testing by team boss Franz Tost as the potential surprise of the season. The same age as Gasly, he has scored 16 of Toro Rosso’s 43 points from 12 races.
Reporting by Alan Baldwin; Editing by Mark Heinrich