Just about every WR in the NFL starts off as a project. Most don't become good to great WRs until their 3rd year in the league. Off the top of my head I can only think of 3 WRs that made big impacts as rookies within the last 20 years or so - Moss, Boldin, Terry Glenn. WRs that hit the ground running are the exception not the norm.
WRs with 120+ fantasy points as a rookie:2009: Percy Harvin- 925 yards from scrimmage, 6 TDs (in 15 games)2008: Eddie Royal- 1089 yards from scrimmage, 5 TDs (in 15 games)2007: Dwayne Bowe- 995 yards from scrimmage, 5 TDs2006: Marques Colston- 1038 yards from scrimmage, 8 TDs (in 14 games)2005: none2004: Michael Clayton- 1223 yards from scrimmage, 7 TDsLee Evans- 928 yards from scrimmage, 9 TDsLarry Fitzgerald- 798 yfs, 8 TDsRoy Williams- 818 yfs, 8 TDs (14 games)2003: Anquan Boldin- 1417 yfs, 8 TDsAndre Johnson- 966 yfs, 4 TDs2002: none2001: Chris Chambers- 872 yfs, 7 TDs2000: noneThat's 11 receivers in the last 10 years who reached the 120 point mark (which would have guaranteed a top-30 finish in 8 of the past 10 seasons). 4 of them reached the 140 point mark (which would have guaranteed a top-20 finish in 8 of the past 10 seasons), and two of them scored 160+ points (Michael Clayton finished his rookie year as WR13, and Boldin finished as WR4). And Colston would have easily hit 160 had he played 16 games.In the decade before (1990-1999), there were 10 120+ point seasons, 5 140+ point seasons, and 2 160+ point seasons (Randy Moss, who was WR1 as a rookie, and Joey Galloway, who was WR14 as a rookie). The decade before that (1980-1989), there were 9 120+ point seasons, 4 140+ point seasons, and 1 160+ point season (Billy Brooks, WR9 as a rookie).Rookies who hit the ground running are not as uncommon as everyone thinks. On average, there's a good rookie every year, a great rookie every other year, and an exceptional rookie every third or fourth year.