While Gavin Henson's return to the international arena threatens to take centre-stage at the Millennium Stadium, Gatland has highlighted Jones' immense contribution in Wales colours since he made his debut 13 years ago.
Jones' feat will unfortunately be achieved at a half-empty ground against the invitational Barbarians, rather than a Test-playing country, but it should not be allowed to diminish his achievement.
"You couldn't meet a nicer guy than Stephen," said Gatland, whose experienced fly-half is a key part of his World Cup plans in New Zealand later this year.
"The number 10 in Wales is probably the hardest position to be. People tend to either support you or they don't, they are in one camp or the other.
"He has been fantastic for us, and the good thing about him is he's still working and wanting to improve his game.
"He knows he is not the finished article and he wants to go out there and perform. You see that motivation in him - he has been a great servant for Wales."
Jones, only the second Wales player after Gareth Thomas to clock up a century for his country added: "The key for me is that I have enjoyed my time in the Wales squad, working with top players and coaches.
"The game keeps evolving, and you never stop learning. But if Saturday is an important day for me, it is a bigger one for the team because the road to the World Cup starts then."
While Jones' World Cup place is assured, 98 times-capped flanker Martyn Williams provides an intriguing sub-plot tomorrow.
Williams was left out of Gatland's Six Nations squad this season, with Dan Lydiate and tomorrow's Wales captain Sam Warburton firmly establishing themselves as first-choice selections.
And Williams' hopes of featuring in a fourth World Cup could be shaped by how he performs this weekend - for the Barbarians.
Gatland added: "It's been a hard one for us. Martyn has been a great servant, and you would love him to get to 100 caps.
"He needs to perform. I was asked the question that if this was New Zealand would they give someone two caps to get to 100 or would they just pick on form? I know what the answer is there.
"I would love to see Martyn reach 100 caps, and if he does perform on the weekend and puts himself in contention for the World Cup squad, he can make 100 caps, but that's up to him.
"I don't think it is about being sentimental, it's about picking for the right reasons. I think we need to be strong on that, and I am sure Martyn would definitely understand that. If he gets a couple and gets to 100, that is fantastic."
The Barbarians, 38-32 conquerors of a shadow England side at Twickenham last Sunday, are strengthened by players like Williams, former New Zealand wing Doug Howlett and Leinster full-back Isa Nacewa lining up against Wales.
And Henson can expect an uncompromising reintroduction to the international game, given the presence of juggernaut Baa-Baas centres Seru Rabeni and Mathieu Bastareaud.
The fixture - officially staged to mark the Welsh Rugby Union's 130th anniversary - has been widely criticised for its scheduling and a contentious WRU decision to award caps.
Gatland though, can still use it as a valuable pre-World Cup exercise, running the rule not only over Henson, but debutant forwards Ryan Bevington and Toby Faletau, while also assessing Warburton's qualities as a possible long-term skipper.
"There is motivation for players to put their names forward for a World Cup squad," he said.
"You look at the Baa-Baas squad, and it is not a bad team they have put out against us.
"It is going to be a big challenge for us, but we want the physicality that Saturday will bring, just to know where we are at for a few players.
"It's important for us that we bring our own intensity. It's going to be tough and physical, but that is what we are looking for."
Wales: M Stoddart (Scarlets); G North (Scarlets), J Davies (Scarlets), G Henson (unattached), A Brew (Newport Gwent Dragons); S Jones (Scarlets), M Phillips (Ospreys); R Bevington (Ospreys), H Bennett (Ospreys), P James (Ospreys), R Jones (Ospreys), L Charteris (Newport Gwent Dragons), D Lydiate (Newport Gwent Dragons), S Warburton (Cardiff Blues, capt), T Faletau (Newport Gwent Dragons).
Replacements: L Burns (Newport Gwent Dragons), S Andrews (Cardiff Blues), A-W Jones (Ospreys), J Turnbull (Scarlets), T Knoyle (Scarlets), R Priestland (Scarlets), S Williams (Scarlets).
Barbarians: I Nacewa (Leinster); P Sackey (Toulon), S Rabeni (La Rochelle), M Bastareaud (Stade Francais), D Howlett (Munster); B James (Clermont Auvergne), S Tillous-Borde (Castres); I Thomas (Scarlets), S Bruno (Toulon), C Hayman (Toulon), I Tekori (Castres), P Tito (Cardiff Blues), J van Niekerk (Toulon), M Williams (Cardiff Blues), S Parisse (Stade Francais, capt).
Replacements: L Ghiraldini (Treviso), D Kubriashvili (Toulon), E Lund (Biarritz), G Smith (Toulon), L Williams (Cardiff Blues), W Mason (Toulon), B Baby (Clermont Auvergne).
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