But quite how much they missed the man now being hailed as a warrior and a terrier has perhaps only become apparent in the last few months.
The versatile Turkey international suffered a ligament rupture in his big toe in the game BEFORE he scored against Liverpool right in front of the Kop 18 months ago.
He played with painkillers that day at Anfield, fired home a beauty to put this side ahead from right-wing but was perhaps a bit loose in defence when Cody Gakpo equalised.
And that was it. Season over - just as he was putting his toe in the water.
But are we only realising now just how much he might have offered in that debut campaign had he been available?
To say as much is to possibly admit to a slight gap in football knowledge.
It seems, certainly if you look at social media, there are people who know everything about every player these days.
Albion linked with a left-back in South America or an under-21 in Scandinavia or Africa?
Someone will post: “Would be a great signing. He has always impressed me.”
But you never quite know how even an international player from a top division who we have seen at major tournaments will adapt to the Premier League over a sustained period.
The high-energy approach of Kadioglu suggested he would thrive. The early appearances perhaps did not.
Then, with Pervis Estupinan about to depart, Albion brought in Max De Cuyper, an attack-minded left-back who looked the pick of the summer business in pre-season.
But Kadioglu has been a regular at left-back since the early weeks of the season and seized the opportunity.
Let's be clear. Estupinan was often excellent for Albion and made plenty of appearances last season before earning a dream move to Milan.
But injury meant we were left waiting to see what Kadioglu would offer in whatever role that would have been.
Like Estupinan and Marc Cucurella before that, he can pop up in different areas. Left-back is a launch pad. He gets forward.
Like both those players at their best, he seems to turn in the same performance every week.
The consistency means there is little to really talk about, so he is rarely mentioned in press conferences.
But, if the next few weeks go as Albion hope they will, his shot against the bar at Brentford might end up being considered the turning point of their season.
Like any full-back, he can be caught out defensively by top-level players in this all-star league.
There were suggestions he might have done more to stop Bukayo Saka ahead of his goal at the Amex.
Maybe Kaoru Mitoma could have done more to help him as well even before Saka produced his value bet of a shot which somehow landed him a winner.
But Kadioglu’s performances for the Seagulls were being discussed in Turkey even before he grabbed the limelight with the winning goal in his national team’s World Cup play-off against Romania on Thursday.
“He’s definitely very important,” Albion boss Fabian Hurzeler said just ahead of the 2-1 win over Liverpool.
“I think it's about consistency. About being there all the time, trying to be intense in wanting to win one-v-one duels, facing a lot of running.”
Intensity is a word many players use when asked about the adaptation of coming to the Prem.
Hurzeler then put a slightly different nuance on the same idea. Resilience.
He said: “Now he gets more and more resilient. Not only out of possession, he also has a big impact on our game in possession.
“He can run a lot. He can fight, he can be very tough and like a small warrior, like a small terrier who's always there and in personal duels.
“That's what we need.”
And resilience is a good word. Even with De Cuyper often on the bench, Kadioglu has played the full 90 minutes in every game since early December with the exception of the 1-1 draw with Bournemouth, when he was replaced on 89.
That list of appearances includes FA Cup ties against Liverpool and Manchester United.
He will look to help Turkey secure a World Cup finals spot when they visit Kosovo on Tuesday.
Then comes the chance to end his season in the manner it deserves.
All of which is a far cry from this time last year.
He admitted: “I was out for seven months and you get a lot of questions – ‘What's wrong, what happened?’ I think a toe injury is always really difficult because you're always on your feet.
“And it's a part of the body that heals slowly. So that was quite difficult.”
We can all look at stats and YouTube clips from other competition for clubs and country.
But the Prem is the ultimate test in terms of playing 90 minutes week in and week out at a high level.
It is a marathon of sprints.
We now know exactly what we were missing.