No way.
Dragon Force Natsu and Ice Devil Slayer Gray (with black mark) barely defeated Mard Geer with high diff.
Both DF Natsu and DS Gray are more powerful than Pre TS Erza or Gajeel in 1 vs 1, tho I could see them being able to solo that form of Erza and Gajeel together. Erza and Gajeel from war arc wouldn't be able to beat Mard Geer.