McAllister has been one of the NFL's most productive running backs since being picked by the Saints in the first round (23rd overall) of the 2001 NFL Draft, rushing for over 1,000 yards three straight years (a first in Saints' history) as the centerpiece of the Saints offensive attack. As of 2005, he ranks second in team record books with 4,194 rushing yards and 31 touchdowns and is first with 22 100-yard games, including a franchise-record nine straight contests in 2003. The Saints are 14-8 when he reaches the milestone, and McAllister has added 165 receptions for 1,262 yards and four touchdowns. In 2003, he finished second in the NFC in rushing and fourth in the league with a career-high 1,641 yards on 351 carries. That total is also second in club history (RB George Rogers, 1,674 yards, 1981). Including the 516 yards on a career-high 69 receptions, McAllister posted 2,157 yards from scrimmage that season to set a club record and rank second in the NFC. All of these accomplishments were a stunning encore to 2002, when in his first year as a starter he led the conference with 1,388 rushing yards, scored 16 TDs and was voted to the Pro Bowl. McAllister is the lone Saints' running back to be voted to the Pro Bowl in consecutive seasons.

McAllister was placed on injured reserve on october 10, 2005, after suffering a torn anterior cruciate ligament in his right knee.