The National Baseball Hall of Fame will announce its class of 2019 Tuesday and, for the first time, it may enshrine someone with a unanimous vote.

Mariano Rivera, arguably the most dominant closer the game has ever seen, is expected to easily make it into Cooperstown. Rivera, who spent all 19 of his Major League seasons with the New York Yankees, amassed a big league record 652 saves.

There has never been a unanimous choice for the Hall of Fame. The closest to get there was Seattle Mariners and Cincinnati Reds legend Ken Griffey Jr. He was voted in with 99.3 percent of the vote in 2016.

Theories as to why no one has been a unanimous pick have varied. One of the most common is that some voters don't like to pick someone in their first year on the ballot. Griffey was inducted in his first year and Rivera is also on his first ballot.

Signs are looking good for Rivera as shown by the ballots that have already been made public. Ryan Thibodeaux is a noted ballot tracker who keeps a spreadsheet of all the votes already revealed. As of Tuesday morning, an estimated 52.7 percent of ballots had been returned and Rivera was named on every one of them.

A player must be named on 75 percent of the ballots to be enshrined.

Edgar Martinez

On the other end, Seattle Mariners slugger Edgar Martinez looks like he will get into Cooperstown in his 10th and final year on the ballot. He's breaking through his own Hall of Fame barrier. He played the majority of his 18-year career as a designated hitter, something that has been considered a detriment to players in the past. 

As of Tuesday morning, he was on 90.8 percent of the known ballots. There would have to be a significant dropoff in the remaining ballots for Martinez to not make it.

Martinez, a seven-time All-Star, has a career .312 batting average with 2,247 hits, 309 home runs and 1,261 RBIs. The annual award to the American League's outstanding designated hitter is named for him.

Roy Halladay

The other player who appears to be a lock is two-time Cy Young Award winner Roy Halladay, who will be in on the first ballot. Halladay finished with 203 wins and a 3.38 ERA over 16 seasons with the Toronto Blue Jays and Philadelphia Phillies.

Halladay pitched a perfect game against the Florida Marlins in 2010. That October, he pitched a no-hitter in the playoffs, beating the Cincinnati Reds in the National League Division Series. One walk in the fifth inning kept him from another perfect game.

Thibodeaux's tracker had Halladay on 92.6 percent of the ballots Tuesday morning.

Halladay's induction will be posthumous. He was killed when the single-engine plane he was piloting crashed off Tampa, Fla., in November 2017. An autopsy revealed evidence of morphine, an amphetamine and Ambien in Halladay's body.

Others to watch

Another player to watch is former Baltimore Orioles and Yankees pitcher Mike Mussina. He was on 81.6 percent of the known ballots, but that could leave him in danger of just missing the cut when all the votes are tallied.

Roger Clemens (71 percent) and Barry Bonds (70.5 percent) both look like they will miss the cut in their seventh year on the ballot. But they should both finish with a higher percentage of votes than last year.

Andy Pettite, Lance Berkman, Roy Oswalt and Michael Young are all in danger of finishing under five percent. That would eliminate them from future ballots.