It came in a 2-0 Championship win at Coventry City on Boxing Day 2007.
Palace were managed by Neil Warnock, against whose Cardiff City side Scannell hopes to reach his Town century.
“He played a big part in my career,” said the 26-year-old who is now in his fifth season at Town and the club’s longest-serving player.
“Neil gave me my debut as a substitute at QPR earlier in the month, and after I came off the bench a few more times, I got that first start.
“I had only just turned 17, so it was great he had that faith in me.
“It wasn’t just me he gave a chance to, and the gaffer was brilliant with the younger lads as well as he experienced players.
“His man-management is excellent, and he’ll have Cardiff right up for this game.”
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An £800,000 buy from Palace during the 2012 close-season, Scannell has made 165 Town appearances in all after 141 for the South London club.
He returned from a hip injury to make his 99th Town start in the 1-1 home draw with Birmingham City last time out.
“I don’t keep count of my games, and when I was told I was nearing 100 starts, I was a bit surprised,” he revealed.
“But as a number, it sounds good, and hopefully I will get play against Cardiff, although nobody takes anything for granted here.
“The manager has made it clear he likes to rotate the squad and we are all used to it now.
“It’s been a bit of a stop-start season for me due to injury, but I have trained well throughout the international break.
“I’m feeling really fit and I’m enjoying my football under David Wagner.
“I want to find some consistency in my performances, and having played in the last match, I want to get a bit of a run going.”