Constantino Rocca, who featured in three Ryder Cups, said the players will struggle to keep their focus if further rain hampers play at Celtic Manor.
"It's difficult for the players who have already had their matches held up," the Italian said as deep puddles formed all round the Twenty Ten course to cause play to be suspended in the 38th Ryder Cup yesterday.
"For those guys, they have played five or six holes, stopped, might have to play for another one or two hours, might have to practise in between – it's very difficult to maintain concentration.
"It is not easy for anyone to maintain concentration when you don't know if you are playing or not playing. For both teams it's difficult.
"Weather like this doesn't help anyone," said the 53-year-old. "I played in the rain many times. You play four or five holes but those holes are terrible.
"The weather can change from sunshine to heavy rain, sometimes wind, and your bag is full of water. It is not easy but if the course is playable you have to play."
Rocca said it was particularly tough to keep the ball in play. "If you find the rough, it's very difficult," said the Italian. "I think especially when you're chipping, you don't know how much water is under the club. But these guys always play in bad conditions and I think they will show what they can do."
Pro's tip: how to play in the rain
By John Hawksworth (Broadcaster and former European Tour player)
At the Ryder Cup, or any tournament, it is in the rain that a caddie really earns his wage keeping everything dry. As an amateur you will have to do everything yourself so the first thing is to have a towel handy to keep the grips dry. Also, it is important to wipe the face of the club before each shot to remove any excess water and, if you use a glove, keep it in a cellophane bag when not wearing it. Keep the ball in a warm pocket, but since the atmosphere is cooler when it is damp, take an extra club, don't grip it too tightly and swing easily. The aim is to keep the ball on the fairway but if you get in wet rough take an extra club – and lie the face open too, since there will be more of a tendency for it to turn over.