Fisher left PNE for Boro at the end of January, ending a three-and-a-half-year stay in Lancashire.
There is a fondness for Fisher from North End boss Alex Neil the right-back having been his first signing in July 2017. So seeing him in the red of Boro will take some getting used to, just as it did with Ben Pearson playing for Bournemouth recently.
Neil said: "I won't lie, seeing Ben Pearson playing for Bournemouth the other week wasn't nice.
"He was a key element in all my team here, Darnell likewise.
“Darnell was a fundamental part of my team, he was my first signing here.
“I always had a good relationship with him. There are some players who you can kick into life – having a bit of aggro with is probably the wrong word – but it is along those lines, and Darnell was one of them.
“I tend to grow close with those kind of players and I grew close with Darnell. I think he’s a really good lad, a really good player who wants the best for himself and for his team. I like that trait.
“We are playing his new team and I hope we win but I hope he goes on and does really well for himself.”
North End signed Fisher on a free transfer from Rotherham United, his capture seen as slightly underwhelming at the time.
He went on to establish himself as the first-choice right-back, making 119 appearances in a Preston shirt.
It did come as something of a surprise when he left PNE for Boro in the last few days of the winter transfer window.
The 26-year-old was in the last few months of his contract and hadn't been offered a new one, unlike some of his team-mates who were in the same situation.
When Boro came calling, North End chose to cash-in rather than seeing him leave for nothing in the summer.
Fisher came off the bench in Boro’s 3-0 win over Stoke on Saturday, that his seventh appearance for the club. The previous six games had been starts.
The Teessiders have work to do to make the play-offs, Neil Warnock’s men currently in ninth place, eight points behind Barnsley in sixth.
After a difficult spell in late January and early February which saw them go five matches without a win, Boro's form has been much stronger of late.
Their last seven games have seen four wins, a draw and two defeats.
Grant Hall, Paddy McNair and Nathaniel Mendez-Laing were on target with the goals in their weekend victory.
North End won the reverse fixture 3-0 at Deepdale in December, Scott Sinclair, Brad Potts and Emil Riis with the goals.
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