Derby boss John Gregory has warned Portsmouth they face a struggle to keep hold of Yakubu Aiyegbeni at the end of the season.

Aiyegbeni scored twice and had a hand in three goals as Portsmouth beat Derby County 6-2 at Fratton Park on Saturday.

The 20-year-old Nigerian was a target for Gregory last summer and spent the pre-season with Derby but he twice failed to obtain a work permit.

Aiyegbeni was able to join Portsmouth on loan until the end of the season from Israel's Maccabi Haifa, due to his recent marriage to a Portuguese citizen.

"Now that Yakubu is playing in this country and in the shop window, I'm sure that there will be quite a few Premiership clubs watching him closely," said Gregory.

"He has great strength and pace and will always cause problems. If he is not scoring himself, he will create for others.

He can bang the ball with both feet, he's got dynamite in his boots. I'm just pleased we've got him Harry Redknapp

"It's sad in a way knowing what might have been for our club had we been able to sign Yakubu.

"He played like that in behind-closed-doors games for us. Now he is doing it against us."

Portsmouth boss Harry Redknapp was delighted to have added Aiyegbeni to their championship challenge, with a view to a permanent deal.

"He has fantastic potential. He is lightning quick, is a powerful lad and can play with both feet," he said.

"He can bang the ball with both feet, he's got dynamite in his boots. I'm just pleased we've got him."