Portland’s magic number to a clinch playoff spot is five, but its lead in the Eastern Division is just two.

The Portland Sea Dogs have one of the best records in minor league baseball at 75-47.

The Binghamton Mets look pretty good, too, at 72-48.

The problem for Portland is that Binghamton is in its division — the Eastern League Eastern Division. Portland holds a two-game lead over the Mets. The Sea Dogs have 20 games to go, Binghamton 22.

Fourteen of Portland’s 20 remaining games are at home, including their game at 7 p.m. Tuesday against the Akron RubberDucks. Tuesday’s game is the first of a six-game homestand, three against the RubberDucks and three against the Richmond Flying Squirrels.

While the Sea Dogs are battling for the division title (and home-field advantage in the first round of the playoffs), they are nearly assured a postseason spot.

The top two teams in each division reach the playoffs, and third-place Trenton (59-63) is 16 games behind Portland.

The Sea Dogs’ magic number to reach the postseason is five (either five Sea Dogs wins, five Trenton losses, or any combination that reaches five).

Akron (66-56) is a contender in the Western Division, 21/2 games behind first-place Richmond, and 51/2 ahead of third-place Bowie.

If Akron’s nickname sounds different, it is. The franchise is under new ownership, which did away with the Aeros nickname.

Tuesday’s game features two of the leading starters in the league: Portland left-hander Brian Johnson (9-2, 1.89 ERA) and Akron right-hander Joe Colon (8-6, 3.20).

Johnson, 23, has been dominant since his call up from Class A in May. He has allowed more than two earned runs in only one start, which was a rare off day on July 7 when Johnson gave up seven runs to the Mets in 21/3 innings.

Since that start, Johnson has made five starts, allowing a total of two earned runs (a 0.51 ERA).

While Johnson leads the league in ERA, Colon is sixth. Both pitchers were named to the Eastern League All-Star Game.

The Sea Dogs will be a little short-handed since Sean Coyle went on the disabled list after spraining an ankle on Aug. 8. Coyle ranks seventh in the league in batting, with a .302 average.

Portland has a history of good hitters, including Daniel Nava, who batted .364 for the Sea Dogs in 2009. Before Tuesday’s game, the Sea Dogs will commemorate Nava’s time here, and with the Red Sox, with a free Daniel Nava bobblehead doll to the first 1,000 fans through the gate.