Clarke heads to his old Stamford Bridge stomping ground this weekend as Albion take on Chelsea, the club where he spent much of his playing career and coached for more than four years.
Clarke missed out on re-signing Blues striker Lukaku, who had a goal-laden loan spell at The Hawthorns last season, on loan in August when a deal was apparently close until Everton beat them to the punch at the last minute.
But the Baggies boss, who will be reunited with his old boss and friend Jose Mourinho for the first time on Saturday, insists there is no lingering bitterness about the way things were handled, especially as Albion added the likes of Morgan Amalfitano, Stephane Sessegnon and Victor Anichebe to their squad.
"What's the relevance? It's gone," he said. "We did good business on deadline day and got in some good players.
"Since we've brought those players in we've picked up 12 points from seven matches, which is a good return. That's all we need to concentrate on.
"There's no point going over old ground that's been covered before. We want to just look forward to the game now. As my mum used to say, there's no point crying over spilt milk.
"I've got a lot of good friends at Chelsea and I look forward to seeing them at the weekend."
Clarke admitted winger Scott Sinclair is unlikely to be back from a long-standing hamstring injury in time for the game against his former club.
"Scott's done a bit of training this week but I think the game's going to come a little bit too early," he said.
"But he's working well and we'll assess him on Friday. He's had three hard days training with the team and we'll see how he reacts overnight and make a decision on whether he travels with us. But it's too early for the starting XI."
Anichebe has fully recovered from a hamstring problem himself but Nicolas Anelka is doubtful with a groin issue.
Right-back Billy Jones (hamstring) joins Zoltan Gera and Ben Foster on the absentee list.