Drmic struck twice after coming off the bench at half-time in Leverkusen's 5-1 thumping of Cologne, helping inspire Roger Schmidt's team to victory after a tough first half.
Cologne hit the front in the fourth minute through Matthias Lehmann's penalty but the home team responded 22 minutes later thanks to Karim Bellarabi.
After Hakan Calhanoglu's free-kick put Leverkusen in front in the 61st minute, Drmic struck in the 79th and 88th minutes before Bellarabi also notched a brace - set up by Drmic - soon after to complete the scoring.
Since joining Leverkusen from Nuremburg before the season, Drmic has made only one start in the Bundesliga but his brace on Saturday took him to three goals for the campaign.
"I've always given my all here and today I was given more playing time. You could say the dam has been broken now," the Switzerland international, who replaced Stefan Kiessling, said.
"It'll do me a lot of good and I'm certainly relieved after scoring both goals. It's a great feeling."
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