Although Merino knew he made the 'right' decision when he left Newcastle in 2018, the 25-year-old admitted it was a 'tough' call to depart after just a year at the club.
"I felt at home there and I'm not lying when I say that," Merino told ChronicleLive. "I felt so welcome by the fans, by my team-mates, by the atmosphere. The city was amazing. I was enjoying just going to the city centre and having a pint or going for a walk and enjoying the people speaking nicely to you. I was feeling great.
"I look back on those times and it was a shame I could not play more games and enjoy the fans and the league a little bit more, but my mindset right now is it was a huge year for me. I learned a lot.
"I'm really sure I'm the player that I am now because of Newcastle and all the experiences that I lived there. I'm really happy that I lived that and I wish all the best for every Newcastle fan.
"The team right now are killing it so I'm really happy for them. Even now, when I watch the games and you see over 3,000 people travelling for an away game - it's crazy! You start to remember those times when you were playing away and you felt like you were playing at St James' Park.
"I still get goosebumps. It was a crazy year for me. I miss those days a little bit, but I'm really happy where I am right now."
Merino also said: "I've grown a lot as a player.
"I'm more of a leader. The maturity that I have now - not only the experience that the minutes of the games give you but the years of experience that you have when you grow up and live different things - has given me a lot of confidence in myself.
"Right now, I feel like I'm a great player. I can help any team win any game. Back in the day, I used to think I had the quality and potential to become a great player. I never doubted myself in that aspect.
"Believing in my capabilities was always key for me and, with time and experience, I'm reaching a good level but this doesn't end here. I want to keep going like this, keep learning from my mistakes, keep improving and become an even better player."