Quarterback guru Jon Gruden has closely examined both Jameis Winston and Marcus Mariota for his ESPN show and believes both could develop into good NFL quarterbacks, but, like a good brisket on the smoker, they’ll need to be brought along slowly.

“They need some seasoning,” Gruden said. “They might need a little bit of time.”

Winston and Mariota, who could go first and second in the NFL draft, which is set for April 30 through May 2 in Chicago, were highly successful at the college level. Winston played in a pro-style offense for Jimbo Fisher at Florida State, while Mariota played in spread attack at Oregon.

“Mariota and Winston are both rookie quarterbacks,” said Bill Polian, a retired six-time NFL executive of the year. “Rookie quarterbacks need time to develop. They do not come in ready-made and tailor-made to play. Andrew (Luck) was an outlier. Peyton (Manning) struggled for the first two thirds of his career. (Robert Griffin III) came into a situation where they built the offense around his skill set and he did fine until he got hurt. But that was a bit of an outlier as well.”

Most teams have not been able to duplicate the success of the Falcons and Ravens had by starting Matt Ryan and Joe Flacco immediately. Both teams were able to win with rookie quarterbacks in 2008 and sustained that winning for a period of time with the Ravens winning a Super Bowl and the Falcons reaching the NFC title game after the 2012 season.

The scrapheap of first-round quarterbacks who’ve been rushed to field includes three-fourths of the quarterbacks selected in the first round of the 2011 draft. The exception has been Carolina’s Cam Newton.

Jake Locker (eighth overall, 2011), Blaine Gabbert (10th) and Christian Ponder (12th) were all unsuccessfully rushed into starting roles. Locker has retired altogether. Gabbert is a backup with the 49ers, while Ponder is trying to revive his career with the Raiders.

Matthew Stafford, the No. 1 pick in 2009, was rushed to the field. He has 35-42 record as a starter and didn’t reach the playoffs until last season.

The wash-out list includes Mark Sanchez (fifth overall, 2009), Josh Freeman (17th, 2009), Sam Bradford (first, 2010), Tim Tebow (25th, 2010), Brandon Weeden (22nd, 2012) and E.J. Manual (16th, 2013).

The jury is still out on last season’s first-round quarterbacks: Blake Bortles (third), Johnny Manziel (22nd) and Teddy Bridgewater (32nd).

If Winston and Mariota are not handled properly, they could join the list of first-round quarterback busts.

“There is just not a lot of patience anymore,” Gruden said. “I’ve seen the NFL chew up and spit out young quarterbacks that I thought were going to be very good.”

ESPN draft analyst Mel Kiper Jr. is conflicted over who’s the better NFL prospect because of Winston’s several off-the-field issues, which include allegations of rape and now a civil lawsuit that alleges sexual battery, assault, false imprisonment and intentional infliction of emotional distress arising out of forcible rape.

Winston was not charged with a crime and Florida State’s decision and appeal found that he did not violate the student conduct code.

“Jameis, I had him up there as the guaranteed No. 1 after his freshman year,” Kiper said. “There was no question that he was going to be the first pick in the draft.”

Then all of his bizarre incidents — not paying for crab legs and yelling vulgar obscenities atop a table in the student union — and brushes with law enforcement came to light.

“The concerns to me are can he be a CEO,” Kiper said. “I still have those concerns based on what happened. There are six or seven issues.”

Kiper believes that Winston is more talented.

“If it wasn’t for the off the field issues, it would be Winston,” Kiper admitted. “But that is factoring into the decision that everybody is making and it’s factoring certainly into the decision that Tampa Bay has to make at No. 1.”

Gruden is also high on Colorado State quarterback Garrett Grayson as a developmental candidate.

“He’s proven that he’s good pocket passer,” Gruden said. “He’s played for two coaches that have been in the NFL, Steve Fairchild and Jim McElwain.”

Polian keeps it real when discussing the top two quarterbacks.

“At this time of the year all we hear is how great they are and how good they are going to be,” said Polian, who will be inducted into the Pro Football Hall of Fame in August. “Six months from now, we’ll hear how hard it is to get used to the speed of the game.”