PHOENIX -- Ken Kendrick never intended to be a major player in the baseball-card-collecting industry. Of course he never intended to become the majority owner of a Major League franchise either.

Yet, today, the managing general partner of the Arizona Diamondbacks is both.

"I kind of backdoored my way into all of this," Kendrick said.

When Kendrick visits the National Baseball Hall of Fame and Museum this summer with his son, Cal, he'll use the front door and he'll also be able to visit part of his baseball card collection, which will be on display.

The exhibit entitled "The Ultimate Set" opened on April 17 and features 25 cards from Kendrick's collection, including the most famous baseball card of all, a T206 Honus Wagner card that Kendrick acquired three years ago for $2.8 million.

"We opened 'The Ultimate Set' during Youth Baseball Week and the early reviews have been terrific.," Hall of Fame president Jeff Idelson said. "It seems that we haves brought out the kid in all of our visitors thanks to Ken's generosity."

While the Wagner card was clearly a big-ticket purchase, Kendrick's interest in baseball cards had a more humble beginning.

"It was nothing special, I was just like all my other buddies at the time collecting cards," Kendrick said. "We played games with them where you could bet cards, we traded them. It was just fun."

It just so happens that the year Kendrick started collecting cards was 1952, which turned out to be a seminal year for the hobby.

"The 1952 TOPPS set is one of the most precious sets in all of collecting," Kendrick said.

Kendrick's top five cards*
1 1909-11 Honus Wagner
2 1952 TOPPS Mickey Mantle
3 1915/1916 Sporting News Babe Ruth
4 1909-11 Eddie Plank
5 1933 Goudey Nap Lajoie
* as ranked by Collecting Sports Legends

Of course he didn't know that at the time. He just bought card packs, played with the cards and put them in old cigar boxes. He did that for about four or five years before his younger brother, Rick, took over and did the same thing.

"We both went on to get interested in girls as teenagers and forget about cards," Kendrick said.

His mother, though, did not. She saved them and in 1990 when he went home to visit her she told him she still had the cards. He had them shipped to Arizona and began to catalog what he had. His goal at the time was to complete the sets that he had and as he traveled for business he would visit card shops in search of the cards he needed.

After spending three or four years filling out the sets, he became known to some of the bigger players in the industry and began to develop an interest in the "elite" cards -- ones that are rare or have significant value.

That interest intensified when he met former big league pitcher and current D-backs broadcaster Tom Candiotti, who had built an impressive collection himself.

"I wasn't focused on collecting sets," Candiotti said. "I didn't care about sets. I wanted the star cards, that was where my interest was."

Candiotti spent 25 years putting his collection together and almost nabbed the T206 Honus Wagner card himself in the late 90s, but a deal he had worked out to buy it for $1 million fell through.

When Candiotti met Kendrick, the two realized they shared a common passion, and for Candiotti, the timing could not have been better. When he joined the organization in 2006, he was looking to sell his collection for a variety of reasons, not the least of which was that having cards that were worth so much money began to scare him.

"I couldn't keep them in my house," he said. "They were locked away in a security deposit box."

Kendrick offered to buy Candiotti's cards and Candiotti realized there was no one he wanted to have them more than Kendrick.

"It was great because Ken really appreciated them," Candiotti said. "He was proud to have them. He also told me if my kids ever wanted to see them they could at any time because the cards weren't going anywhere. He wasn't selling them. I can't tell you how much that meant."

There was another reason Candiotti was so happy for Kendrick to have the cards.

"It was perfect because Ken had the capabilities to get the Honus Wagner card," Candiotti said. "That was what was missing."

Not for long, as Kendrick nabbed it a year later.

"I had a big leg up in doing what I now have done because I had Tom's, plus my own, and I could merge them," Kendrick said. "And then [the opportunity to buy the Wagner card] came along and A plus B plus C ended up creating the deal that is at Cooperstown."

Of the top five most important cards in the hobby, according to the book "Collecting Sports Legends," Kendrick's owns every one. How rare is his collection? Well his Honus Wagner card is given a Pro Sports Authenticator grade of eight -- on a scale of 1-10. Of the 30 known Wagner cards in existence it's the only one to be rated above a four.

The No. 2 rated card is Mickey Mantle's 1952 TOPPS rookie card. There are three of them in existence that have gotten a grade 10, and Kendrick owns two.

In other words, no one has a card in the Top 5 that has a higher grade than the version Kendrick owns.

"Obviously no one could have a collection like I have," Kendrick said. "There's only one."

Kendrick, who has never sold one of his baseball cards, declines to get into the monetary worth of his collection and instead talks about the value that can't be measured in dollars and cents. Like when he showed 14-year-old Cal the Wagner card for the first time after purchasing it.

"I told him someday this collection will belong to you, and it could be something you can remember me by," Kendrick said, his eyes lightening up with the memory of what came next. "A couple of hours later he comes back and says, 'Daddy, you know the cards? I just want you to know I would never sell those cards.' That's the best part of this whole story for me -- that my kid at 11 was that mature to really get what all this means. Who knows what will happen in the future, but I'm not a seller of cards, I'm not a dealer, I'm a collector of cards."