The 31-year-old had one year left on his previous contract and would have been able to leave for nothing in the summer of June 2021.
Reguilon broke into the Real Madrid first team in the 2018-19 season, making 22 appearances and moving ahead of the Brazilian left back Marcelo in the pecking order.
"The result didn't meet my expectations, I was thinking about 20.50s or so," said Xie.
"I believe in Arsenal. We can achieve big things together. We have something exciting here and I believe the best is yet to come," he added.
As expected, Barcelona star Lionel Messi heads the list, with Juventus forward Paulo Dybala and Inter Milan striker Lautaro Martinez also included.
Pakhtakor goalkeeper Suyonov was sent off in the 65th minute and Sanzar Kuvvatov was brought on to take his place. But almost instantly, the Uzbek side rallied at the other end of the pitch and replied with a goal, as substitute striker Eren Derdiyok blasted in the rebound after Dragan Ceran's initial effort was saved.
The Gunners only finished eighth in the Premier League last season, but their FA Cup win secured them a place in the UEFA Europa League for the 2020-21 campaign. Enditem
Both SIPG and Zall started the game aggressively, but neither side managed a goal in the first half. SIPG broke the deadlock in the 59th minute when Australian striker Marko Arnautovic jumped to find the net with a power header. 11 minutes later, Australian midfielder Aaron Mooy scored his first goal in the CSL for SIPG and extended the lead to 2-0.
"I think it's an amazing feeling. I was waiting for this moment for a long time and I am very, very happy to be here," Thiago told the Liverpool club's website.
In the first stage competition held in Milton Keynes, England, 31-year-old Xiao won the group decider against Iran's Hossein Vafaei 3-0.
Bakambu and Augusto helped Beijing grab another score by exchanging their roles in the 46th minute. Bakambu converted a header with the assist of Augusto to make it 2-1.