Sam Bradford’s play through his first four starts has been as instrumental in taking the Vikings to 5-0 as anything else the team has done. There’s just no way that the Vikings front office and coaches, despite their belief in his ability, could have thought Bradford would join this team after two weeks of studying the playbook and play the best football of his life.

Before his first four starts with the Vikings, the best four-game stretch Bradford had put together was from Week 8 through Week 11 during his rookie year in 2010 with the then-St. Louis Rams.

Over that stretch, he threw for 983 yards, eight touchdowns, one interception and completed 67.9 percent of his passes for a 100.2 quarterback rating.

Through his first four starts this season he has thrown for 990 yards, six touchdowns and no interceptions and completed 70.4 percent of his passes for a 109.7 quarterback rating.

Coach Mike Zimmer tried to explain earlier this week just how it’s possible for a quarterback like Bradford to perform like this, and he said he believes there is no disadvantage to having to quickly learn a new offense.

“I don’t know that it’s a disadvantage. … We’ve been throwing more receivers in the mix, and so he has gotten to learn all the other receivers as well,” Zimmer said. “I don’t feel like he has played at any kind of disadvantage. I think the offensive coaches have done a great job with getting him prepared.

“The one thing about Sam is that he will communicate the things that he likes to do, and if we have a play in the game plan that he doesn’t like, he’s going to say it. He’s going to tell Norv [Turner], and we get rid of the play. So, we try to do things that he’s comfortable with, even though it has been a short period of time.”

Best start in years

Easily the greatest season a quarterback has ever had in Minnesota was Daunte Culpepper’s 2004 campaign, when he set franchise records for yards (4,717), touchdowns (39), completions (379) and quarterback rating (110.9), all of which still stand.

Bradford, of course, has a long way to go if he’s going to maintain his current stellar stats, but as of now he’s on pace for 3,720 yards, 30 touchdowns, 330 completions. If he sustained his current QB rating, he would be on pace for one of the greatest seasons in Vikings history.

When it comes to starting the season, though, Bradford’s first four starts stack up with the best starts of Vikings quarterbacks in recent years.

Culpepper’s first four games in 2004 were unbelievable, with 14 touchdowns compared to one interception, 1,341 yards passing and a QB rating of 126.0, but even then the Vikings were 3-1 in Culpepper’s first four starts that season.

When Brett Favre joined the team in 2009, he also started 4-0, but his numbers were actually slightly lower than Bradford’s. He had 837 yards passing on a 68.0 completion percentage with eight touchdowns and one pick for a 104.6 rating.

Randall Cunningham in 1998 was also incredible, throwing for 978 yards, 10 touchdowns, zero interceptions and a 127.8 rating through his first four games in what became a historic Vikings season, and one of the best offensive seasons in the NFL.

Still, if you want one big difference between those starts and Bradford’s, consider this. The 1998 squad had Robert Smith as its lead back, and he averaged 121.0 rushing yards per game. In 2004 with Culpepper, the Vikings averaged 113.9 yards rushing per game, and Culpepper himself was extremely mobile. The 2009 squad had one of the great seasons by Adrian Peterson as he rushed for 1,383 yards and the team averaged 119.9 yards rushing per game.

The Vikings this year are averaging 70.6 rushing yards per game. The run game is improving, and if that continues Bradford’s numbers have a chance to get even better.

Looking to Eagles

It has only been six weeks of the season, but has any trade in recent memory worked out as well for both teams — and been as risky — as the Eagles’ and Vikings’ deal to send Bradford here for a first-round draft pick and a conditional later-round pick?

Bradford has stabilized the best team in the NFL after the presumed starter went down with a horrific knee injury one week before the season.

Moving Bradford cleared the way for Carson Wentz to step in as a rookie starter for the Eagles, and he has been phenomenal.

Now the two will get to face each other in a surprisingly important game Sunday.

Through Week 5, Bradford was second in the NFL in QB rating while Wentz was sixth at 103.6. He has also been an incredible game manager for the Eagles, though they fell 27-20 to Washington on Sunday.

The Eagles had their bye week last week so it’s interesting to consider each QB through his first four starts of the season. Bradford had the better QB rating. Wentz had more yards (1,007-990) and touchdowns (7-6). Wentz had just one interception, which is one more than Bradford had, and Bradford’s completion percentage was slightly higher at 70.4 compared to 67.4.

But there’s no question for Vikings and Eagles fans that this trade, which many questioned at the time, has turned out tremendously for both squads.

More positive signs

Why are the Vikings clicking? Three other reasons:

• Xavier Rhodes grabbed the third interception of his career in Week 4, which seems low, and he only has three pass deflections this year, but the Vikings coaches have praised him as their best cornerback for the job he has done against such receivers as Odell Beckham Jr. and DeAndre Hopkins this season.

• Linval Joseph has 25 tackles, which was tied for the second most in the NFL through five weeks. His three sacks are already tied for the second-highest total of his career.

• Adam Thielen is having a breakout season. Following his 127 yards receiving vs. Houston before the bye, USA Today wrote, “Thielen has been solid when called upon and has earned more looks going forward.”

Jottings

• The Vikings recently signed tackle Jake Long, and the former No. 1 overall pick will make only $624,705 as he tries to come back in the NFL after some bad injuries. That number is a prorated amount of the NFL minimum, but the Vikings also have stipulated if Long ends up on injured reserve, they only have to pay half that contract. Long has earned about $71 million over his nine-year career.

• With star cornerback Joe Haden sidelined by a groin injury, the Browns started rookie Briean Boddy-Calhoun on Sunday and the former Gopher led Cleveland with seven tackles in a 28-26 loss to Tennessee.

Sid Hartman can be heard weekdays on 830-AM at 6:40, 7:40 and 8:40 a.m. and on Sundays at 9:30 a.m. shartman@startribune.com