Former Crystal Palace midfielder Alassane N'Diaye, ex-Bristol City winger Tristan Plummer and Maltese striker Aman Verma were all present at Fratton Park on Thursday as they tried to earn deals.
Whittingham revealed that N'Diaye particularly caught his eye
"I thought he showed some good touches," he told the Portsmouth News.
"We've asked him to come in and train with us. He showed that he's played football at a decent level for Palace. You can tell he's a footballer."
He did however go on to concede that a deal may be unlikely to be reached before the end of the season. Plummer also impressed Whittingham, although he had doubts over his fitness.