Allagui joined Mainz on loan this summer after failing to convince Luhukay he could figure frequently in his plans. His first game back at Mainz, where he had a two-year spell in 2010/12, could come at the Olympiastadion and Luhukay is wary of him.
"Allagui is a threat for us," he said. "Many players get an extra kick against their former clubs. Hopefully that won't happen against us. I wish Sami all the best, only maybe after this weekend."
Allagui is looking forward to his return, and to the prospect of playing more frequently for his new - and old - club. He moved from Mainz to Berlin in 2012 and now feels he is "back home".
"A few days ago, I was wearing blue and white, now I'm wearing red and white," he said in the Frankfurter Rundschau. "Two weeks ago, I went into one dressing room ahead of the Bremen game, and on Saturday I will go into the other one.
"I had plenty of good offers, but as soon as I heard Mainz were interested, my heart started beating faster. It took me just five minutes to consider the offer. I knew what I could expect here and how the club works. I love the way they play football here. It's all just perfect. I'm fit and I'm ready."
Mainz coach Kasper Hjulmand has said there is a "good possibility" that the 28-year-old will start, and he could certainly do with goals from the Tunisian, who will plug a gap left by the sale of Eric-Maxim Choupo-Moting to Schalke.
Hjulmand's side are still searching for their first win of the domestic campaign after drawing twice and losing in the DFB-Pokal. They did beat Asteras Tripoli in the first leg of the third qualifying round of the Europa League in July, but the Greek side turned the tie around in the second leg to dump Mainz out.