Oak Hill Country Club, near Rochester, N.Y., has been a familiar stop for men’s professional golf for decades: Since 1956, it has hosted three U.S. Opens, three P.G.A. Championships and a Ryder Cup.But when the P.G.A. Championship returns to Oak Hill on Thursday for the first time since 2013, the East Course will be different than it was for some of the elite tournaments it has hosted. In recent years, the club brought in Andrew Green to interpret and restore some of Donald J. Ross’s original design from the 1920s.Green, who has also worked on overhauls at other major championship courses — Congressional Country Club, Inverness Club and Scioto Country Club — can sometimes be seen as “fairly radical,” as Jack Nicklaus, who grew up playing at Scioto and won the 1980 P.G.A. Championship at Oak Hill, put it recently.In an interview this spring, though, Green said he had regarded the Oak Hill project as an opportunity to reemphasize Ross’s approach, which includes unorthodox shapes for greens.“I took the most pride in being able to reestablish a few of the golf holes that had been lost to time,” said Green, who, to try to decipher the thinking of Ross, who died in 1948, studied his writings, pencil sketches and formalized drawings, as well as a selection of historical photographs.An archival map shows both the East and West courses at Oak Hill Country Club.Oak Hill Country ClubRoss’s influence at Oak Hill had faded over the decades, particularly with the work of the uncle-nephew duo George and Tom Fazio in the 1970s. Their changes, by Oak Hill’s own account, “created a more challenging layout for the several major championships that followed” but also promoted “significant criticism since they did not fit” in Ross’s original design. Hundreds of new and ultimately overgrown trees, the club also said, had shifted the course away from Ross’s vision.“As the evolution of the golf course had occurred, players and critics and the golf world had always felt there was a disconnect within the golf course itself,” Green said. “Really, the primary goal was to reinfuse Ross and make the entire course feel as if it had always been there.”No. 5: Little PoisonPar 3, 180 yardsNo. 5 emerges from a thicket of sand, rough and steep slopes. Evan Schiller, Oak Hill Country ClubThe par-70 course measures 7,394 yards, 231 yards more than the 2013 P.G.A. Championship but 151 yards less than how Augusta National Golf Club played during last month’s Masters Tournament. With the rough expected to be challenging and parts of Oak Hill strikingly narrow, even after many trees were removed, Green thinks the P.G.A. Championship could show “an interesting balance to see if the guys who can really bomb it and gouge it out have a leg up on everyone else, or if someone that really finesses it around the golf course will still be able to mount a good run.”An early glimpse at finesse will come at No. 5, where a long tee shot will all but stifle hopes for a birdie and could even make tapping in for par a formidable challenge. Positioned between the fourth hole and what was No. 15, the target emerges from a thicket of sand, rough and steep slopes. Green and his colleagues envisioned No. 5, where the green has two tiers, as a midiron test.Oak Hill Country Club“It will be a bit of a nervy shot, but aiming for the center of the green and trying to make a putt would be my suggestion,” Green said. “The whole vision for it was to play off of what Ross had on his original sixth hole.”No. 6: Double TroublePar 4, 503 yardsNo. 6 offers several hazards.Evan Schiller, Oak Hill Country ClubAfter an escape at No. 5, the hole Green believes is now the course’s most perilous awaits.Allen’s Creek runs alongside the right side from the start, forcing a player to choose between the risk of dropping his tee shot into the water — but perhaps also getting a better angle into the green if he avoids the hazard — or facing a longer second shot.“The green allows for a ball to be run into the approach, if they need to with a longer club or if they get in trouble off the tee,” said Green, whose restored course has water in play on six holes. “The green itself, front hole locations are fairly accessible, but the back right location is very demanding, very tough to get to. My guess is they’ll probably put the hole back there and move the tees forward on a certain day during the championship.”Oak Hill Country ClubPart of the challenge is that the creek does not simply run in a straight line off the tee, or even away from it. Instead, it ultimately moves diagonally across the approach and then up to the left side of the green.No. 6, Green said, was naturally the trickiest hole, given its placement and the parcel of earth on which it sits. With the fourth, sixth, seventh and eighth holes slotted in a relatively narrow sliver of earth, he assumed that Ross had “tried to find the most unique way to set those golf holes kind of side by side, and the result of that differentiation from hole to hole was what we got on the sixth.”Green added: “He had four golf holes that, on a very flat piece of ground, would be potentially very much the same way, but the way he utilized the ground and the creek made them all night-and-day different, and he was a genius at that. It was a very awkward piece of property that he had to work with — it wasn’t just a giant rectangle — and so the way he created the variety he did is just mind-blowing to me.”No. 13: Hill of FamePar 5, 623 yardsThe longest hole on the East Course travels uphill.Desiree Rios/The New York TimesThe longest hole, No. 13, could be a showcase for the equipment that is helping top players drive the ball farther than ever. The hole goes uphill, bringing players toward the clubhouse, with Allen’s Creek making an appearance at around the 325-yard mark.The evolution of equipment, Green predicted, will entice top players to hit the ball over the creek, which has been a relatively rare occurrence through Oak Hill’s history.“We added a new tee, but I still think the golf course at times will be set up where players would be tempted to play over that and get home in two,” Green said.Water is not a threat beyond the creek, but the vicinity of the newly reshaped green has two of Oak Hill’s 78 bunkers.No. 15: The PlateauPar 3, 155 yardsIf the tournament moves to a playoff, No. 15 will be a part of it.Evan Schiller, Oak Hill Country ClubWhen Jason Dufner won the 2013 P.G.A. Championship at Oak Hill, the 15th hole included a man-made pond stationed menacingly near the putting surface and a rock wall.“It was a very dramatic shot for major championship golf and TV,” Green said, “but it wasn’t very good for member play, and it didn’t represent anything Ross would have done.”So the pond is gone. Missing left will send a ball into a bunker that guards the left side. Missing right will have the ball moving away from the target in short grass, forcing a player to make a delicate shot onto the skinniest portion of the green, which is narrow left to right and deep front to back — maybe, Green said, a club-and-a-half difference, front-to-back.Oak Hill Country Club“It will be a very demanding shot in order to both control distance and spin to get close to the hole locations,” Green said.If the tournament moves to a playoff, No. 15 will be a part of it, along with the 14th and 18th holes.No. 18: Goin’ HomePar 4, 497 yardsThe green on No. 18 sits on the edge of a steep hill.Evan Schiller, Oak Hill Country ClubEyes always turn toward the 18th hole at any major championship. For Green, it was the one he fretted over most.“Unfortunately, that green really kind of stuck out a little bit in its shape as being very modern and out of character with the others,” Green said.Now the green, which sits on the edge of a steep hill that a player should look to carry with a second shot, has been extended on the right side and made deeper. The left side is shallower, front to back, and there are effectively three distinct surfaces within the green to place the hole.Oak Hill Country Club“Hitting a good drive is critical — absolutely critical,” Green said of the hole, where the fairway width can be as tight as 20 yards. “There are some very deep bunkers down the right-hand side that will make it very difficult to get home.”A player who successfully hits from the fairway to get his ball onto the zone of the green where the hole is will have a shot at a birdie. Otherwise, Green said, “it will be quite a dramatic putt to make that three.” More