"We have Luke Joeckel, and he spoke very highly of him," said Caldwell, speaking Thursday afternoon at Lucas Oil Stadium.
Caldwell confessed he is genuinely intrigued with Manziel, the Texas A&M quarterback who won the Heisman Trophy as a freshman in 2013 and rode a roller-coaster calendar year to arrive at the 2014 NFL Scouting Combine as one of the most polarizing prospects in the draft.
The Jaguars drafted Joeckel, a left tackle and Manziel's teammate for two seasons with the Aggies, No. 2 overall in 2013. Jacksonville has the third overall pick in May, and Caldwell, among others on the scouting staff, witnessed Manziel's electric playmaking ability for himself last season.
The Jaguars' bid to fill the quarterback position failed multiple times and prompted coaching and regime changes that ushered in Caldwell and first-time head coach Gus Bradley 13 months ago.
"We'll treat Blaine like any other player," Caldwell said, "until we decide it's not in our best interest or he's beat out."
If not Manziel, the Jaguars are in line for another quarterback and will consider veterans in free agency or trade.
Caldwell isn't paying mind to the recent draft history -- hint: it's not good -- of the Jaguars and believes the foundation built last April on the strength of Joeckel and safety Johnathan Cyprien is a big stride in the right direction.
"Cyp probably didn't get the credit he deserves," Caldwell said of the Florida International product, a standout at the 2013 Senior Bowl drafted as an in-the-box presence who proved more dynamic and versatile than even the Jaguars expected.
Joeckel was limited to seven games because of an ankle injury.
The recent losing trend can be traced to chronic failure in the first round of the draft.
Wide receiver Justin Blackmon (fifth, 2012) played 20 games and has been suspended twice. Caldwell said at this time life, not football, has to be Blackmon's focus and any reunion will be considered only after the first part is in order.
Gabbert and defensive lineman Tyson Alualu (10th, 2010) haven't met expectations, nor come anywhere close. One of two first-round picks to prove any tangible worth to the franchise in the past decade was Eugene Monroe, a left tackle who started 76 games but was traded to the Baltimore Ravens in October 2013. The other, tight end Marcedes Lewis (28th, 2006), is in decline and could be released to save cap money this spring.
Defensive end Derrick Harvey (eighth, 2008), safety Reggie Nelson (21st, 2007) and wide receivers Matt Jones (21st, 2005) and Reggie Williams (ninth, 2004) are other bold-faced names on the franchise "miss" list.
While Manziel might be intriguing, Jacksonville is in no position to gamble and risk prolonged poor results. Counting a 4-12 record last season, the franchise is on a profound six-season slide since David Garrard, Fred Taylor and Ernest Wilford led the 2007 Jaguars to the playoffs.
Caldwell said Thursday that part of the rationale behind trading Monroe was adding to a purse of draft picks -- now at 10 -- for a class that lines up as one of the deepest in decades.