Spanish centre back Tiri, who is returning after three years, was on Monday named along with star Indian defender Sandesh Jhingan in a 27-member squad announced by ATK Mohun Bagan here.
Tiri was part of ATK's ISL-winning side in 2016 before switching to Jamshedpur FC, while Jhingan has been the most high-profile signing of the season.
It remains to be seen who will partner the duo in the backline with coach Antonio Lopez Habas having former Mumbai City defender Subhashish Bose also at his disposal.
Then there's the trio of Pritam Kotal, Sumit Rathi and Prabir Das who have been retained.
During their practice session at Benaulim Stadium, the Spanish gaffer was seen paying extra attention to their defence to get a perfect combination for the duo of Tiri and Sandesh.
"For me, every player is important. I want to build a team of players who give his best when picked.
"Being a long league, we have to be careful of injury card problems. So it's about keeping players ready for every position," Habas said.
The Habas-coached side conceded only 19 goals in 21 matches during their triumphant campaign last season and with Tiri and Jhingan on board, their defence will be the one to watch out in the upcoming season, when they will also represent India in the AFC Cup.
Fijian star forward Roy Krishna is likely to wear the captain's arm band but Habas, who is known to rotate his skipper, did not reveal any name.
The squad has seven foreigners in Tiri, Roy Krishna, David Williams, Edu Garcia, Javi Hernandez, Carl McHugh and Brad Inman.
Playing for the first time as a merged entity, ATK Mohun Bagan will face FC Goa in their only practice match on November 14, six days before the tournament opener against Kerala Blasters.
Goalkeepers: Arindam Bhattacharja, Dheeraj Singh, Avilash Paul, Arsh Anwer Shaikh, Aryan Niraj Lamba
Defenders: Tiri, Sandesh Jhingan, Subhasish Bose, Sumit Rathi, Pritam Kotal, Prabir Das, Boris Singh Thangjam
Midfielders: Brad Inman, Ningombam Engson Singh, Carl McHugh, Pronay Halder, Michael Regin, Sheikh Sahil, Javi Hernandez, Glan Martins, Mohammad Fardin Ali Molla, Michael Soosairaj, Edu Garica and Jayesh Rane
Forwards: Roy Krishna, David Williams and Manvir Singh.