On a sunny but cool morning at Dove Mountain in Arizona's high desert, Swede Pettersson scraped past American Rickie Fowler after 19 holes and Spaniard Fernandez-Castano beat Italy's Francesco Molinari 2up.
Pettersson will next meet Ireland's Shane Lowry, a shock 1up winner over world number one Rory McIlroy, while Fernandez-Castano will face American Charles Howell III, who upset three-times winner Tiger Woods 2&1.
The only previous time the top two players were eliminated from the first round of the elite World Golf Championships (WGC) event was in 2002 when Woods and Phil Mickelson were both knocked out.
Based on the seedings, there were 15 upsets in the 32 first-round matches which took just over 50 hours to finish after driving snow led to play being suspended on Wednesday after only three-and-a-half hours of action.
A total of four inches of snow had fallen by Thursday morning but, weather-permitting, the second round will be completed on Friday, with the third round and quarter-finals set for Saturday in a bid to get the tournament back on track.
Thankfully, fears of a possible frost delay on Friday morning never materialised and play began on time in the two incomplete first-round matches.
Pettersson was 1up on Fowler after 17 holes overnight but the American made it all square with a conceded birdie at the par-four 18th where he struck a superb approach to inside two feet.
However Fowler lost the match with a bogey on the 19th hole, the par-four 10th, after his drive ended up well right in the desert scrub.
It was the only the second time in four Match Play appearances that five-times PGA Tour winner Pettersson had reached the second round.
Fernandez-Castano and Molinari were all square overnight after 15 holes but the Italian folded quickly with bogeys on 16 and 18 to gift the Spaniard a spot in the second round. (Reporting by Mark Lamport-Stokes; Editing by Frank Pingue)