The Hoops were unable to make the most of their opportunities in the eventual 3-0 loss to AC milan on Tuesday night which ended their campaign in Europe for the 2013/14 season.
Dutchman Vennegoor of Hesselink, who scored plenty of goals for the Glasgow giants between 2006 and 2009, believes the loss of Gary Hooper to Norwich City in the summer has negatively affected Celtic's attack.
"There are good players in that squad but they lost some important ones during the summer," he told Sky Sports News.
"If you look at the squad and the resources Neil Lennon has, he did a good job by qualifying for the Champions League group stages, but you can always use a fresh injection of players into your squad.
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