Zach Ertz's quest for greatness led him to three of the NFL's all-time best as mentors this offseason. But his search for one wouldn't have happened had he not met Ronnie Lott.

A mutual friend brought Lott to dinner one day in January. Ertz, of course, knew of the former 49ers defensive back. He grew up in the San Francisco area and attended Stanford, but he had never met arguably the best safety of all time.

Lott also knew of Ertz. He was familiar with the Eagles tight end and his promising first two seasons, but also that something was missing.

"He was like, 'You had a good first two years, but what's separating you from being a great tight end?' " Ertz said last week during an interview with The Inquirer. "And I said, 'Well, I need to consistently be on the field more.' And he said, 'Well, what's keeping you off the field?'

"And I said, 'Just consistently blocking.' He's like, 'This offseason, why don't you reach out to someone to help you with your blocking?' I was like, 'Wow, why did I not ever think of this?' "

Ertz did his homework and was told that retired offensive line coach Hudson Houck still trained players. So he called Houck, who mentored Hall of Famers Anthony Munoz and Bruce Matthews at Southern Cal and coached the great Cowboys lines of the 1990s, out of the blue. Soon after, they spent two weeks together in San Diego working on blocking.

Ertz said his offseason focus on blocking was relayed to Eagles coach Chip Kelly. The third-year tight end, who will join the majority of the Eagles at the NovaCare Complex Monday when voluntary spring workouts begin, said that he's eager to gauge his progress but that he isn't taking anything for granted.

"I wanted the coaches to be happy, but at the end of the day I wanted to do this so I could personally improve," Ertz said. "Hopefully, that makes us better as a team. We lost a lot of guys and I think there's an opportunity for me to maybe take the next step.

"Last year there was so much hype about, 'Oh, Zach Ertz is going to have a breakout season.' This year there are no predictions. There are no statements. I didn't make any statements last year, but this year I feel like whatever happens happens."

Ertz's time with Houck was just one part of his offseason plan. He spent a month focusing on strength training, another on circuit training and additional time on mixed martial arts training. He also sought out former tight end great Tony Gonzalez, who instructed Ertz on the importance of preparation and tenacity.

The 24-year-old Ertz's goals are high. He said he wants to be mentioned someday alongside Gonzalez and others in the NFL pantheon of tight ends. But he knows he can't get there if he's playing only 50 percent of offensive snaps, as he did last season.

Only Rob Gronkowski (1.36) and Travis Kelce (1.29) had as many yards receiving per play among tight ends as Ertz (1.20) in 2014. Among active tight ends, only Gronkowski (1,873), Jimmy Graham (1,866), Antonio Gates (1,353) and Jason Witten (1,327) had as many yards receiving as Ertz (1,171) in their first two seasons.

But aside from Graham, each played significantly more than Ertz, who often watched from the sidelines as Brent Celek played on first and second down.

There's ample reason, though, to believe that Ertz will finally become a focal point of Kelly's offense. He caught a franchise-record 15 passes against the Redskins in the penultimate game of last season. And when asked to explain last month how he'll compensate for the loss of wide receiver Jeremy Maclin, Kelly prominently mentioned Ertz.

"I think he's still growing, and I think Zach will be the first one to tell you that," Kelly said at the NFL meeting. "I think he's working extremely hard in the offseason at continuing to get better. I still think there's a big jump that can occur with him from Year 2 to Year 3."

Ertz's numbers (from 36 catches for 469 yards in 2013 to 58 for 702 in 2014) and playing time did increase, but not as much as expected. Still, he finished 12th in receptions and 11th in yards despite playing more than 300 fewer snaps than the average of the league's top 12 tight ends.

When Ertz did play 75 percent or more of the snaps - at the Colts and Redskins - he had his best pass-catching games. In Washington, Kelly used him in a variety of ways, including flanking him outside and motioning him inside. Ertz said that he hopes it was a sign of things to come.

"It's not a goal of mine to only play 45 percent of snaps," Ertz said. "It's to be on the field for every single play. That was the goal this offseason."

Ertz spent last offseason gaining more strength to aid his efforts to become a better blocker and had improved from his rookie year. But a few early-season struggles in run blocking last season, particularly against the 49ers, limited his opportunities to mostly on passing downs.

But it wasn't just Kelly's preference for Celek in certain situations that cut into Ertz' pass-catching opportunities. Gonzalez, for instance, was never a top-line blocker, but his receiving skills and the threat he always posed made it imperative for coaches to keep him on the field.

Ertz was fourth in targets last season behind Maclin, Jordan Matthews and Riley Cooper. With Maclin gone and no one receiver likely to step into that hole, Ertz - like Gonzalez - could become the first or second option for whoever ends up at quarterback.

Gonzalez retired last year as the most prolific tight end in NFL history. His consistency over 17 seasons remains unparalleled.

"He has this 'Routine of Greatness' he calls it and he would consistently do this routine each and every day, whether it was watching film or his pre-practice routine, or post-practice routine," said Ertz, who drove to Orange County to meet with Gonzalez. "He had it down where he thought it was the best routine anyone should have. And then he also taught me the value of the mental aspect of the game. He thinks people should train their mind as much as their bodies."

Ertz may have to prepare himself for only a marginal increase in snaps. The Eagles offense is run-based and the addition of running backs DeMarco Murray and Ryan Mathews could further tilt the scale. And Kelly's affinity for the 30-year-old Celek, who is entering his ninth season, is well known.

But Ertz' untapped potential is undeniable and the Eagles won't always have him under contract.

"I think it has been tough," Ertz said of playing behind Celek. "Brent, first and foremost, has been so supportive of me. . . . We have a great relationship. But this year I hope there will be more instances where we're on the field together.

". . . I know he's got two more years on his contract and I've got two more years on mine. Hopefully, we finish this out together, and hopefully, I sign here for a long time."

jmclane@phillynews.com

@Jeff_McLane