Crewe caretaker boss Dario Gradi believes Calvin Zola and Clayton Donaldson can become one of the most feared strike partnerships in League Two.

Zola is among the top scorers in the division with 10 league goals and the Congolese has netted 13 times in all competitions this season.

Donaldson has only recently returned from a lengthy lay-off after breaking a leg in August but has scored in each of his last two appearances.

"They are definitely a handful. They are doing fine at the moment but I think that there is still more to come from both of them," Gradi told BBC Radio Stoke.

"Calvin is one of those players that sometimes you are not happy with, but you would rather have playing for you than against you.

"Clayton is very quick. I've still to see the best of him and I haven't seen a lot of him to be honest, but he seems to be building a good understanding (with Zola)."