It earned the Senegal international a three-match ban from the FA and a fine of two weeks' wages by his club.
De Zeeuw was praised at the time for showing remarkable restraint in the face of such a deplorable act, and 10 months on, he doesn't want the incident over-shadowing the build-up to the eagerly-awaited derby.
The Dutch centre-half accepts they'll never be best of friends, but hopes it's the football which grabs the headlines on Sunday.
He told the Evening Post: "I've played against Diouf since the spitting incident when Bolton played at Portsmouth near the end of last season, and that was a very odd experience.
"It's safe to say we won't exchange birthday cards, but what happened is gone now and it's time to move on.
"Diouf had a lot of bad Press over it, I'm sure he got a lot of stick from his own manager Sam Allardyce, and people won't forget about it easily.
"I didn't shake him by the hand last time and I'll have to think what to do about that this time.
"People must have a chance to improve themselves and learn from their mistakes, that applies to everyone.
"I think I surprised myself about how calm I kept at the time, but as I've said, it's in the past now and I'm just approaching Sunday as a game of football.
"Diouf is a good player and we have to be careful with him as he scores goals and sets up chances for other players.
"I will be looking at him like that, not because of the spitting thing."
Whether Diouf starts the game at the JJB remains to be seen as the former Liverpool forward was dropped to the bench for last week's match – ironically against Portsmouth – after scoring just once in six games.
De Zeeuw, though, is a certain starter, as his partnership with Stephane Henchoz at the heart of the defence is a major plus for Latics as they find their feet in the Premiership.
Both are past their 30th birthdays – de Zeeuw is 35 and Henchoz 31 – but the skipper is confident their legs can stand up to the pace of the top flight.
He said: "Players can go on for longer these days as they look after themselves better and their clubs do too.
"Me and Stephane had never played together until I came back to Wigan, but we seemed to click from day one.
"Our defending, though, has not just been about us two because the full-backs Leighton Baines and Pascal Chimbonda have played very well so far.
"The team are on a good run at the moment, with the wins against Sunderland and West Brom, the draw with Middlesbrough, and then last Saturday's victory at Everton.
"But we must stay focused and continue to try to pick up points whenever we can."
Meanwhile, Republic of Ireland manager Brian Kerr has ended David Connolly's exile from international football.
Latics striker Connolly, 28, has been named in a 24-man squad to face Cyprus and Switzerland in critical World Cup qualifiers next month.
Despite 40 caps to his name, Connolly has not played for Ireland since the country's devastating 2-0 European Championship qualifying defeat to Switzerland in October 2003.
The Wigan ace was effectively one of the fall guys for Ireland's failure to reach the finals in Portugal, earning his last call-up just under a year ago, only to withdraw through injury.
Said Kerr: "I have good reports on him because he has made a bright start at Wigan and he looks like his old self."
Latics have confirmed their Carling Cup date with Watford will be on Tuesday, October 25, with prices cut to £10 and £5.