The Reds' 31-goal double Player of the Year will be turning out for Barca when his biting ban is over at the end of October after the two clubs agreed a £75 million deal earlier this month.
Suarez signed a new contract to become the club's highest-paid player of all time back in December and stated his ambition to fire the Anfield outfit to the Champions League, but the Uruguayan striker departs with Europe's premier competition back on the agenda with the Reds next term.
Allen, who was answering a Q&A session on Twitter as part of the club's tour of the United States, the Wales international admitted that the allure of moving to Camp Nou was one that his former teammate couldn't turn down.
"Disappointed [Suarez chose to leave]. He’s world class but you always sensed if Barca or [Real] Madrid came in, he’d find it difficult to turn them down," he said.
Allen also revealed that his idol growing up was France legend Zinedine Zidane, and interestingly revealed that Real Madrid's Luka Modric was the best player he had lined up against.
He added:"My idol? It was actually Zinedine Zidane. He was my favourite player and I used to watch him every weekend.
[The best player I've played] with… is Stevie (Steven Gerrard). I haven’t actually played against him so I can’t say him twice, so against probably Luka Modric."
Finally, the former Swansea City star claimed that £25 million playmaker Adam Lallana has impressed him the most out of the club's new arrivals.
Brendan Rodgers has spent around £60 million on Emre Can, Rickie Lambert and Lazar Markovic and Lallana, and it is the England international who has always caught his eye, although he did reserve a word of praise for £10 million midfielder Can.
"[Best signing?] Tough question! All of them in different ways," said Allen. "Lallana, I’ve played against quite a lot & I’ve always admired him. You can see [Can] has all you need for British football. He’s strong & powerful but also technically good."
The Reds will meet Manchester City, Olympiacos and AC Milan during their tour of the US.