In 2007, Adrian Peterson went from more than 5 yards per carry in the first half to a dismal 3.114 yards per rush over the final 8 games. He followed that up with 1,760 yards (4.8 YPC) and 10 TDs in 2008.
In 2002, Deuce McAllister only averaged 3.584 yards per carry in the second half...clearly he "hit the wall and was overworked", right? He followed that up in with a 1,641-yard (4.7 YPR) 8 TD season in 2003.
In 2004, Clinton Portis struggled to only 3.633 yards per carry in the second half. In 2005, rather than regressing, he put up 1,516 yards rushing (4.3 per carry) and 11 TDs.
In 2007, Portis (again) averaged just 3.644 yards in the second half, and delivered 1,487 yards (4.3 YPR) and 9 TDs in 2008.
In 2002, Edgerrin James saw his second half fall to 3.669 per carry. He followed that up in 2003 with 1,259 yards (4.1) and 11 TDs.
In 2009, Rashard Mendenhall "was gassed" and only churned out 3.768 yards per rush in the second half. He put up 1,273 (3.9) and 13 TDs this year.
In 2008, Frank Gore averaged just 3.837 yards in the second half, he followed that up with 1,120 yards (4.9 YPR!) and 10 TDs in 2009.
In 2009, MJD "lost his explosiveness" and only managed 3.916 yards per rush in the second half. He delivered 1,324 (4.4 YPR) and 5 TDs last year (in less than 16 games).
In 2005, Thomas Jones couldn't muster 4 yards per rush in the 2nd half (3.959) but delivered 1,210 yards (4.1 YPR) and 6 TDs in 2006.
In 2009, Adrian Peterson averaged just 3.993 yards in the second half, but delivered 1,298 and 12 this past year.