Staying healthy, making plays defensively and effective relief pitching are the primary ingredients to finding a heady mixture that leads to baseball’s playoffs.

Where are the injuries? Which teams have too many players who can’t make steady defensive contributions? Does a team have effective one-inning pitchers for the last three innings of games?

Baltimore had a precarious two-game lead over Boston when this week began. Toronto was a just an eyelash in back of the BoSox. And the New York Yankees were a vulnerable fourth place team with a sub-.500 winning percentage.

Baltimore is missing seventh-inning relief specialist Darren O’Day. Outfielder Hyun Soo Kim has a leg injury. Shortstop J.J. Hardy has missed two months with a stress fracture, but has returned.

Boston has lost closer Craig Kimbrel to a leg injury and catcher Blake Swihart is out indefinitely.

The Blue Jays don’t have outfielder Jose Bautista, infielder Ryan Goins or pitcher Marco Estrada, all disabled with injuries.

New York misses Aaron Hicks (.197 batting average) and oft-injured infielder Mark Teixeira (.186 average) is troubled with an injured foot.

With lineups that score the East Division’s most runs, Baltimore, Boston and Toronto have managed to stay on each other’s heels.

The Orioles have the superior defense with four gold glove candidates on their infield. Hardy won’t be given a gold glove because he hasn’t played enough, but Manny Machado, Jonathan Schoop and Chris Davis are excellent fielders. Davis has become just as valuable for his glove as he is with his offense.

The Red Sox don’t usually beat themselves with atrocious defense but can’t equate Baltimore’s unusual quality. Toronto plays at home on artificial turf, a surface that rewards athleticism and quickness . . . and the Blue Jays aren’t missing those qualities in many spots.

With its aging players all too evident on defense, the Yankees can only make up ground with improved offense from nearly every starter and the continued stellar pitching from one-inning specialists Dillon Betances, Andrew Miller and Aroldis Chapman.

If O’Day returns in form to the Orioles, they can almost match New York’s late-inning artists with Brad Brach and Zach Britton giving them one shutout inning after another. Britton has saved or won every game where he has been given a lead.

Boston and Toronto can’t match late-inning specialists with the Orioles and Yankees. And Kimbrel’s absence means Kojo Uehera is now the Red Sox closer. Roberto Osuna closes for the Blue Jays and he’s not Britton nor Chapman.

Concerning the four teams and their stating pitching, Boston made a preemptive strike when it acquired Drew Pomeranz from the Padres. That move keeps ineffective Clay Buchholz in the bullpen and gives manager John Farrell a rotation of Pomeranz, Rick Porcello, David Price, all-star Steven Wright and enigmatic Eduardo Rodriguez.

Toronto can counter with J.A. Happ, Marcus Stroman, R.J. Dickey and Aaron Sanchez but badly misses Estrada. Middle relief in Toronto is a sore subject.

Being mired in fourth place in its own division means the Yankees need more than Masahiro Tanaka as a starter with some consistency. Even though he just 5-7 with a 3.94 earned run average, CC Sabathia has become the second most-trusted starter — since Michael Pineda is 3-9 with a 5.56 ERA, Ivan Nova is 6-5 with a 5.18 ERA and Nathan Eovaldi is 7-6 with a 5.11 ERA.

If New York still considers itself a viable playoff contender something has to be done about its arson-charged group of starters.

And then there” Baltimore . . . with Chris Tillman and little else. Kevin Gausman (1-6 record), Dylan Bundy (three home runs allowed in short work in his first start), Yovani Gallardo, Vance Worley, Ubaldo Jimenez, Tyler Wilson, or Mike Wright are hide-the-women-and children starters on too many nights.

Home runs buoy Baltimore’s offense, but it scored only nine runs in a three-game series at Tampa Bay.

Toronto has Oriole-killer Edwin Encarnacion as well 2015 MVP Josh Donaldson and budding star Michael Saunders to guide its offense.

The Red Sox have David Ortiz going out on a grand scale and can count on Mookie Betts, Dustin Predroia and Xander Bogaerts for offensive fireworks. Jackie Bradley, Jr. won’t keep up his offensive pace, but Hanley Ramierez, Brock Holt and Travis Shaw are all dangerous in Fenway Park.

New York’s lineup can be pitched to, but if Jacoby Ellsbury, Didi Gregorious and 39-year-old Carlos Beltran can all stay healthy then the Yankees ain’t dead yet.

Health. Defense. The bullpens. Will teams make trades to acquire what they see as help? Or will they take their chances on the players they believe can be kept off the disabled lists?