It is sure to be a high-octane occasion at the Millennium Stadium with Cardiff guaranteed a huge and boisterous support in their own city. QPR, for their part, are reported to be taking some 30,000 fans of their own.
It is not the first time that Stephen has encountered the Bluebirds on their own patch - he featured in QPR's 2-1 win at Ninian Park in March and made something of an impression on the home manager.
"I can tell you he has already played at Cardiff for QPR and they won," recalled David. "I spoke to Lennie Lawrence on a coaching course last week and he told me that the boy did very well.
"He signed a new contract before the end of the season, his father came over from Ireland and we sat down and it was all done sensibly.
"I would love him to do well.
"He's a good player, blocks well and has good pace. The Academy staff that knew him well before he got to reserve team level know that there is potential there for sure to come out.
"He'll cope well with Cardiff, although I have already seen enough. If he does well in front of thousands in a high tension game then he will have gone up another notch in his own mind."
In an earlier loan spell at Southend United this season, Stephen played in what he describes as his favoured central defensive position, while at QPR he has featured as a right back. David feels that it is difficult to say what his long-term position might be.
"As a central defender maybe people will say he is short of an inch, while he has got good energy which is an asset as a right back getting forward.
"Very hard to say, because we have got Dean Marney as well who can get down that right side quite well. He covers well as a right back, sometimes when you put centre-halves on the flanks they are good at spotting danger.
"I've known teams who have literally played four central defenders across their back four and have played quite rigidly - whereas other teams like their defences to have more flair going forward. It depends what you are seeking."
Stephen Kelly will line up for QPR against Cardiff in the Division Two play-off final this afternoon and David Pleat is sure that he is more than up to the challenge.