Celtic ended their 2021/22 SPFL season with the best defensive record in the league having conceded just 22 goals in 38 games.
To further highlight their defensive strength, the Hoops faced fewer shots on target (76) than any other side in the top flight.
One figure that played a big part in Celtic's title winning campaign at the back was Carl Starfelt.
Signed during the previous summer transfer window from Rubin Kazan on a four-year deal for a reported fee of £4m, the centre-back quickly became a prominent figure for Postecoglou.
Throughout his debut campaign, the Sweden international made 49 appearances across all competitions and played more minutes in the league than any other outfield player.
With the second-highest number of interceptions (42) and tackles won (30) to his name, Starfelt also had the joint-second highest average of clearances (3.5) and joint-highest average for aerial duels won per game (4.2) in Celtic's ranks.
This highlights just how much of a capable defender he is and how significant he was for the Hoops this term.
Now that the campaign has drawn to an end, the summer transfer window will give Postecoglou the chance to potentially make some more changes to his squad so they can progress.
One figure that could potentially fit in the side well and possibly make a formidable defensive duo with Starfelt is Mohanad Jeahze.
The Hoops were linked with a reported £2m move for the Hammarby left-back, who has been labelled as a "class" player by Darijan Bojanic, last month.
With eight league appearances to his name this season, the defender has racked up the highest number of interceptions (18) and second-highest number of tackles (13) in Hammarby's squad.
This shows how much of a tough defender he is and how he could be a solid fit next to Starfelt to make Celtic stronger on the left side of the defence.
Despite the current Celtic defender already showing his defensive talents, having another defensive full-back next to him, such as Jeahze, could make Postecoglou's side an even tougher side to play against.
Taking into account how the Hoops will be facing off against some of Europe's top teams in the Champions League next season, having some extra defensive reinforcements would not be a bad thing for the Parkhead club as they'll be aiming to regain the SPFL title as well.