Discussing the potential need for reinforcements, Emery told reporters: "If we can take one player to help us at centre-back, I think it's a good option".
"The transfer (window) is not easy... I prefer to use, if we can, a specialist centre-back".
It remains to be seen how quickly the 33-year-old Koscielny can get back to his best after almost seven months on the sidelines, while Konstantinos Mavropanos, 21, is still out with a troublesome groin injury and hasn't played all season.
With Rob Holding effectively out for the season with his ACL injury, Shkodran Mustafi pertaining hamstring issues and Sokratis Papastathopoulos suspended, the recently recovered Laurent Koscielny is the only fit natural centre back Emery has at his disposal for this weekend's clash against Southampton.
We can use other players in this position, like sometimes Monreal and Lichsteiner.
Arsenal were already toying with the idea of signing a striker in January with Danny Welbeck expected to be sidelined for some time after breaking his ankle last month.
Emery said he was likely to field an inexperienced starting XI, with the club having achieved their objective of finishing first in Group E.
Arsenal midfielder Emile Smith-Rowe has scored in two of his last three appearances in the Europa League, with the first of those coming in the reverse meeting against FK Qarabag in October. There are starts for Joe Willock, Bukayo Saka, Ainsley Maitland-Niles, Carl Jenkinson and Eddie Nketiah.
"Our demand is very big". Tomorrow our objective is to win, we will give players chance to take responsibility and confidence.