MANKATO – Why didn't Andre Smith become a top-flight NFL offensive tackle during his Cincinnati days? The question left one of the league's most candid head coaches momentarily speechless.

There was an um, a pained sigh and 11 seconds spent searching for the right words on Saturday afternoon before Vikings coach Mike Zimmer settled on, "I have some ideas, but I don't want to share them. It wouldn't be good."

But Smith wouldn't be here in Minnesota if Zimmer didn't believe in Smith — and the Vikings coaching staff — enough for the team to give Smith a one-year prove-it contract.

And after the retirement of longtime right tackle Phil Loadholt essentially ended what would have been one of training camp's most interesting competitions before it started, Zimmer needs the mercurial former top-10 draft pick to stabilize a critical position on the team's reshuffled offensive line.

If Smith doesn't … um, sigh, it wouldn't be good for the Vikings.

It's not that the 29-year-old right tackle didn't play well at times during his seven seasons with the Bengals, five of which coincided with Zimmer's tenure as Cincinnati defensive coordinator. For whatever reasons Zimmer did not want to share publicly, Smith was inconsistent, at times maddeningly so.

Injuries, weight issues and a rookie-year contract holdout prevented Smith from finding his footing the first two years after the Bengals picked him sixth overall in 2009. But from 2011 and 2013, he missed only two games and started to live up to the promise he showed as a unanimous All-America at Alabama.

In 2012, Pro Football Focus graded Smith as the NFL's fourth-best offensive tackle overall. He was a free agent after that breakthrough season, and not only did the Bengals allow him to reach the open market, they waited several weeks before he settled on a three-year, $18 million contract.

Asked about his roller coaster first few seasons, Smith, more or less, said things happen.

"It's football," Smith said. "I just happened to break my foot twice, but I bounced back from that and played really good [from 2011 to '13]."

But Smith, who was well-liked on a personal level by Bengals teammates and coaches, was healthy for only nine games in 2014 and watched Cincinnati select a pair of tackles with their first two picks in the 2015 draft.

In a candid interview with the Cincinnati Enquirer last August, Smith said he rededicated himself to football because he was "tired of being mediocre." He started 14 games last season, but the Bengals were ready to move on.

Smith remained unsigned until the second week of free agency in March. Zimmer said this spring that he thinks Smith's reputation probably was the reason why others teams didn't immediately pounce. Smith said he signed a one-year, $5.5 million deal with the Vikings in large part due to Zimmer's presence.

"I had a better opportunity to prove myself here in Minnesota and play for somebody that is actually going to push me and make me get better," Smith said.

So far, Smith is definitely being pushed. Second-year pro T.J. Clemmings, who started every game at right tackle last season after Loadholt tore an Achilles' tendon, are alternating days at that position. And new offensive line coach Tony Sparano is trying to coax a mean streak out of Smith, and most of the other Vikings offensive linemen, on these steamy Mankato afternoons.

"I know Tony is going to push him and drive him and keep on him and keep working him. I don't know if that's what he needs," Zimmer said. "He really is a good athlete. His career started out [poorly]. He had a broken bone in his foot and he was overweight and all that. I think he's matured quite a bit. I still think he's got a lot of good football in him."

Veteran cornerback Terence Newman, who played with Smith in Cincy, agrees.

"I thought he was a great tackle when I was in Cincinnati. But if you're a true competitor, you're never going to be satisfied," Newman said. "Good is the enemy of great, and you see a lot of good players fizzle out because they are satisfied with that. I know Dre is not one of those people."

The Vikings don't need Smith to be great. Getting the guy Zimmer saw from 2011 to '13 would suffice.

Barring an upset from Clemmings, they will be counting on Smith to be in shape and locked in as one of Teddy Bridgewater's most pivotal protectors. His performance will be critical because the biggest key to the Vikings potentially becoming legitimate Super Bowl contenders is the quarterback's continued development.

No doubt Smith is a gamble. But Zimmer knows what he is getting into, even if he won't chat about it, and clearly feels Smith is worth a roll of the dice.