They have slipped behind the other two members of Portugal's Big Three
Between the 2002-03 season and 2012-13, FC Porto were hugely dominant on home soil.
As Leicester City fluctuated between the Premier League, Championship and League One, Porto won nine titles in that time span including a run of four leagues in a row and then another of three in a row.
While Portugal has a Big Three, until the last 2-3 years, Porto had the edge on record champions Benfica and Lisbon giants Sporting Clube.
However, as they prepare to take on Leicester in the Champions League group stages, Porto have slipped back behind the other Big Three.
In 2013-14, Porto finished third, before bouncing back to second in 2014-15 and then dropping back down to third again last season when they finished a huge 13 points behind second placed Sporting.
This season after six games of the Portuguese domestic season and Porto are third behind the other members of the Big Three, having already lost 2-1 away to Sporting.
What kept Porto ahead of the pack for so long had been an ability to buy raw talent like Radamel Falcao, Jackson Martinez and James Rodriguez from the South American market for relatively modest fees. That trio cost the club in the region of €20 million. Yet they were sold for gross fees of about €120 million. It proved to be a business model that worked for the club. Those three are just an example as you could also mention names like Hulk and Joao Moutinho who commanded large transfer fees.
Porto's goalkeeper Iker Casillas reacts after Copenhagen scored a goal during a Champions League group G soccer match between FC Porto and FC Copenhagen at the Dragao stadium in Porto, Portugal, Wednesday, Sept. 14, 2016. (AP Photo/Paulo Duarte)
As Portugoal.net founder and Portuguese football expert Tom Kundert once told us, their scouting networks are among the most extensive around.
"The sporting director at Porto did a really interesting interview a couple of years ago when he said they've got 180 scouts scattered all over the world and they have what they call a shadow team, which means they have two players identified for every position in the team and so they know that when one player goes, they already know they have their target. So it's just a matter of putting that into place," he told Newstalk during the 2014-15 Champions League campaign.
However, they clearly haven't replaced the talent sold with the same level of player that they had in the Hulk-Falcao-Rodriguez era.
Aside from the 22 players out on loan including last season's top scorer Vincent Abubakar who has gone to Besiktas until the end of the season, the current squad does not have the same ring to it as the one of old.
Yacine Brahimi is one player that Premier League clubs - Everton were linked with a big-money move - would have interest in, given the Algerian winger's talents.
However, Leicester still face a tough task even at home because of Porto's experience as a club when it comes to Champions League level - something the Foxes do not possess.
But Claudio Ranieri and his side can take heart from the fact that Porto were held to a draw by FC Copenhagen in the group opener at the Dragao stadium.