Louis Picamoles says his time at Saints made him 'grow as a player and as a man'.
But the France star admits the opportunity to finish his career at Montpellier and the financial rewards the club can provide proved simply too strong to resist.
On Wednesday, Saints announced that they had 'reluctantly agreed' to sell Picamoles to the Top 14 giants for a 'significant transfer fee'.
Picamoles had moved to Northampton from Toulouse on a three-year deal last summer and quickly became a stand-out player for Jim Mallinder's men.
The 31-year-old won both the players' player and the supporters' player of the season accolades after a stellar campaign in green, black and gold.
But with the FFR (French Rugby Federation) and Montpellier desperate to bring him back to France, Picamoles wanted to cut short his stay at Saints, who eventually agreed to accept the big bid that was made for his services.
And reflecting on his time at Franklin's Gardens, Picamoles said: "I had a great year. I've learned a lot of new things, new discoveries, a new way of working.
"There is a different mentality, a different approach to events.
"It made me grow as a player and as a man.
"I made a lot of progress and I enjoyed a good off-season, which is sometimes difficult in Top 14, even if it is changing, with new measures taken for international players."
On the move to Montpellier, Picamoles, who has penned a three-year deal, said: "I have never hidden the attachment I have for this club.
"I do not really know if I thought I would come back one day, but the opportunity has been realised, and it is something strong for me to return to the club that formed me, eight years after leaving.
"Inevitably, it reminds me of many memories, and it gives me a lot of joy and confidence for the future!"
So how did the deal come about?
"Montpellier approached me to know if there was the desire, on my part, to return to France," Picamoles explained.
"This coincided with the desire of the FFR to recover the French internationals in the Top 14.
"I left for three years in England, but I seized the opportunity that was presented and that it was difficult to deny at 31 years old.
"Montpellier is my city, it is the club that made me become the player that I am today.
"It's a way of buckling the loop. I come for three years, it will probably be my last contract.
"It was important for me to finish my career in Montpellier, and it was also important for my family.
"I met my wife in Montpellier and we see our life after rugby here.
"We must think of the sequel, and for my family it will be easier than in England.
"Everything was put together so that this decision could be made quickly, and I am happy to have gone to the end of the process."
Picamoles insists he would have rejected the opportunity to move had it not been Montpellier who came calling.
And he is hoping the progress he made at Saints can help him propel his new team to great heights.
"It's a different rugby (in England)," Picamoles said. "There is a lot of rhythm in the Premiership. This is an area where I have had difficulties in the past.
"It allowed me to make progress on some shortcomings that I could have. But I can still improve and I think the new coaching team of Montpellier can help me.
"I am pleased with my English experience, although it was shorter than I imagined. But life is made up of opportunities.
"I would not have asked myself if it was another club. But everyone knows my attachment to the MHR, which is a club that has many values, and I do not think they have disappeared.
"I want to join in the long term with this club and do beautiful things in the very near future."