"The squad we have now is a very good one but to go all the way in the Champions League you need incredible strength in depth," said Shepherd.
"You cannot have a big enough pool of world class players at the highest level and we know we need to add to ours.
"Nobody here is hanging around to see what happens. We have to plan for a Champions League campaign even though nothing is cut and dried at this stage of the season."
But Shepherd admitted Champions League qualification could prove vital.
"The money we would stand to gain from playing in the Champions League would have a major bearing on our summer investment," he said.
"It is likely that the guaranteed income it would bring would be reflected in our transfer dealings."