Leonsis and the star forward have been together a decade without winning a title.
"The consistency he's brought is really historic," Leonsis said at a news conference during the team's development camp. "He plays hard all the time."
"We're in it together," the owner added, "and he knows we're committed. He can sense it and see it."
After failing to make the playoffs during the 2013-14 season, Leonsis got a new general manager (Brian MacLellan) and new coach (Barry Trotz). The Capitals also added a pair of defensemen -- Matt Niskanen and Brooks Orpik -- via free agency.
Last season they improved, making the Eastern Conference semifinals and building a 3-1 series lead over the Rangers before falling in overtime of Game 7.
The Capitals have again been active in the offseason. Within a 24-hour period they signed free-agent right wing Justin Williams -- a three-time Stanley Cup winner -- and traded with St. Louis for right wing T.J. Oshie.
"I'm really proud of the job Mac and the front office ... and Barry did," Leonsis said.
Ovechkin turns 30 in September but is coming off a year in which he led the league with 53 goals.
"Don't take Alex Ovechkin for granted," Leonsis said. "I think that happens sometimes. You see him all the time and there's this repetitiveness about his greatness. When people from outside the organization come in -- I think you heard that with Justin Williams -- this is the best player in the league."
Leonsis also owns the Washington Wizards, and he went through a heart-wrenching few days in May when his NBA team was also in the Eastern Conference semifinals. In Game 5 of the Capitals' series against the Rangers, Washington led with less than two minutes left. But then New York scored to tie the game and won it in overtime.
"This loss really hurt a lot," Leonsis said.
"We were a couple of minutes away from going to the (conference) finals, and I also was watching in the suite the Wizards playing in Atlanta," he added. "There was just this one minute when I said, 'Wow, we're going to the finals, and the Wizards are going to come home up 3-1,' and literally, like that, the Wizards lost and then the Caps had to go to Game 6."
The Wizards also went on to lose their series.
"It was just a real reminder of how tough this is to craft a championship caliber team," Leonsis said.