An old baseball adage used to say the teams in first place on July 4 would win the pennant. Of course, that was well before the advent of five playoff entries in each league.

The current format for determining postseason berths, combined with our shorter attention span, demands a different approach.

So now that the season has passed another notable milestone in Memorial Day, here’s a look at which teams have legitimate aspirations to play in October, which are merely along for the ride and which are somewhere in between.

Shoo-ins

Houston Astros, Boston Red Sox, New York Yankees, Washington Nationals, Cubs, Los Angeles Dodgers.

The Astros’ offense has yet to shift into overdrive, but their rotation is the majors’ best, with a 2.44 ERA that’s a full run lower than anybody else in the American League. Houston has the makings of baseball’s best team.

The Red Sox and Yankees will likely be nipping at each other’s heels the rest of the season, with the loser having to settle for the crapshoot that’s the one-game wild-card playoff. That could be a cruel fate.

Washington has gone 12-6 since Anthony Rendon returned to the lineup May 5, and the club is reasserting itself as the class of the National League. The season debut of second baseman Daniel Murphy should come soon, further fortifying the Nationals’ flanks.

The Cubs have been lurking in the NL Central rather than assuming command, but their talent level and plus-77 run differential – twice as high as the front-running Brewers – suggests they’ll take over the lead at some point.

Starters Kenta Maeda and Walker Buehler are thriving for the Dodgers, who have won eight of 10 and will welcome Clayton Kershaw back to the mound Thursday. Los Angeles has weathered the storm, thanks in part to a feeble NL West.Strong contenders

Cleveland Indians, Milwaukee Brewers, Atlanta Braves, Los Angeles Angels.

The bullpen’s wretched performance keeps holding the Indians back, so they’re lucky that in the AL Central a .500 record is more than enough for first place. Still, Cleveland badly needs Andrew Miller to return to health and to his old form.

Brewers relievers have gone in the opposite direction, shaving nearly a run and a half from last year’s ERA to lead the NL with a 2.45 mark, making up for the starters’ 4.21 ERA. But how sustainable is that bullpen work?

The Braves are breathing a sigh of relief now that the knee injury sustained by rookie phenom Ronald Acuna Jr. does not appear to be serious. He and leadoff man Ozzie Albies, who is tied for second in homers in the NL, have been the catalysts of Atlanta’s productive offense.

The Mike Trout-Shohei Ohtani show is lots of fun to watch, but to secure a wild-card spot the Angels will need the likes of Kole Calhoun (.391 OPS), Ian Kinsler (.511) and Zack Cosart (.707) to pick up the slack.

Fighting chance

Seattle Mariners, St. Louis Cardinals, Philadelphia Phillies, Colorado Rockies, Arizona Diamondbacks, Pittsburgh Pirates, New York Mets, San Francisco Giants, Tampa Bay Rays, Minnesota Twins.

The Mariners have gone an AL-best 11-3 since Robinson Cano was sidelined by an injury, which was followed by a suspension for PED use. The emergence of James Paxton as a staff ace has proved a boon, but Felix Hernandez continues to struggle and it’s fair to question whether Seattle has the talent to end the longest playoff drought in major American sports.

Improved starting pitching – a 3.02 ERA compared to 4.13 last season – has kept the Cardinals afloat during Yadier Molina’s absence, but they’ll need a strong return by their star catcher and for Matt Carpenter to continue his recent surge to make a move.

Under the guidance of rookie manager Gabe Kapler, the second-place Phillies are authoring one of the best stories of the early part of the season with a 29-22 record. At this point last year they were 17-34. Can the prosperity last?

The Rockies, Diamondbacks and Giants failed to exploit the Dodgers’ multiple injuries and consequent stumbles. Now all four teams are bunched up together, a mere four games separating the first from the fourth, and Los Angeles is coming on hard.

The Twins, sorely lacking in offensive punch, remain alive because the Indians haven’t run away with the dreadful AL Central. The Pirates, Mets and Rays, on the other hand, are finding out hovering around .500 doesn’t do them much good in their respective divisions.

Hopeless

White Sox, Miami Marlins, Cincinnati Reds, Baltimore Orioles, Kansas City Royals, San Diego Padres, Texas Rangers, Detroit Tigers, Toronto Blue Jays, Oakland Athletics.

Kudos to the A’s and Tigers for not performing nearly as poorly as many figured, with Oakland staying above the break-even mark despite a rotation and run differential that would suggest otherwise. On the flip side, the Rangers and Blue Jays should soon be looking to unload veterans in exchange for prospects after playing below even modest expectations.

As for the White Sox, Marlins, Reds, Orioles, Royals and Padres, well, they are who we thought they were.