TEMPE, Ariz. -- The reason Carson Palmer received so much rest during organized team activities, minicamp and training camp has been apparent in the Arizona Cardinals' 2-2 start.

He has set career highs in yards, dropbacks, attempts and completions through the first four games of a season and is ranked second in the NFL in passing yards with 1,282, just behind New England's Tom Brady. Palmer is second in the league in completions with 108 and leads the NFL in dropbacks (201) and attempts (183) -- all while being sacked a league-high 17 times.

Carson Palmer leads the NFL in drop backs (201) and attempts (183) this season. Joe Camporeale/USA TODAY Sports

A year ago, when Palmer put up middle-of-the-road numbers in these four passing categories through the first four games, his throwing arm began to tire by midseason. Coach Bruce Arians implemented a resting program that began last November with Palmer sitting out Wednesdays, and it has continued into this season. The goal of resting Palmer was to extend his arm strength and stamina through the season.

His heavy workload through a quarter of the season will test that, but Palmer doesn't think his strong start is related to the rest.

"It's early," Palmer said. "We have been down and we haven't had leads where we have been able to run the ball. I don't know if we have had a lead yet. So, that's part of it. Losing David [Johnson] is part of it. You get away from the run a little bit quicker. I think those two things factor in more than rest in practice."

What you need to know in the NFL

• Statistics

• Scoreboard

• 2017 schedule, results

• Standings

The Cardinals have led this season, albeit rarely. They were ahead against Dallas in Week 3 until late in the second quarter, and led Detroit in Week 1 until early in the fourth quarter. Otherwise, Arizona has been playing from behind or tied, leading to more passes.

Palmer said the 45.75 passes he's averaging per game "are much less than I throw in practice."

Regardless, Palmer's numbers are the highest they've been this early in a season, at age 37.

"He's tough," Arians said. "He's as tough as nails. We know what we've got."

If Palmer keeps up his pace for yards, dropbacks, attempts and completions, he'll shatter his personal bests in each.

He's on pace for 5,128 yards (4,671 was his previous high), 432 completions (373), 732 attempts (597) and 804 dropbacks (700).

If Palmer reaches his projected attempts, he'll set the NFL single-season record. His projections on yards and completions would be the No. 5 and No. 13 highest totals all-time, respectively.

"Carson's having a phenomenal year," wide receiver Larry Fitzgerald said. "If you're looking at the numbers, he's producing like he's always produced."