Tim Gavrich,
The main difference between Pebble and Merion is the generally cooler air and wind influence on the exposed nature of much of the routing at PB which leads to higher scores potentially. Merion, unless it is a freakish week, will generally be warm and not have that pronounced a wind influence.
The Poa greens, when bumpy, also increase the difficulty in going low at PB... many pros go into deep whining mode and get frustrated at Pebble.
Potts,
The rough will matter. Merion's rough can get extremely dense and lush. The ball tends to really settle and nestle there when it gets super penal. Hercules can't just chunk it to a foot out of that stuff. I've caddied in many tour events watching the best in the world up close and personal and the real nasty rough has them ALL crying Uncle...even Tiger. Sure, they'll pull it off once it a while, but don't kid yourself, harsh lies get them plenty!That rough at Congo was candy compared to what Merion will serve up.
Another factor that traditional U.S Opens have not had recently is firm fairways that call for real shaping and thought when hitting and landing your tee shots. When have you seen balls really kicking and bounding directly into rough areas...not often (Pebble, while firm, had very sparse rough and many areas were shaved).
Firm fairways used to be a big part of the examination...that's been absent of late. The weather and lack of undulation or sloping fairways at many of the venues is partially to blame, however here again the watering, pre-event, tends to the moist side. You can't dry it out once it's soft...it's all up to mother nature. Merion has a number of canted, undulating fairways that if firm will present problems to players, even hitting 3 woods and long irons/hybrids. The difficulty of staying in the fairway is far greater when firmness is present in the landing areas. That increases the chance of finding the beastly rough...which if ungraduated...will wreck havoc on any player.
Merion's test is all down to the moisture and weather...the turf condition and set-up being sound. If it's firm...it will be an epic week. If it's soft... the drama will be more subdued.
I'm hoping for some fire in the old girl that week wilth the Bob Marley ruff!
Cheers,
Kris