ST. PETERSBURG, Fla — Through three postseason games, what looked to be a weak link for the Yankees has not been.

For the first four months of the season and right up until Aug. 3, the Yankees were expected to upgrade a bullpen that looked as if it needed help, and then they didn’t. In a stunner, GM Brian Cashman subtracted rather than added, putting his faith in the incumbents and mostly internal options.

Many of those options did not work out. Clarke Schmidt pitched in one game before returning to the injured list. Fernando Cruz is on the 60-day IL. Luis Gil’s stuff did not play up. They brought in Michael Fulmer, who did not pitch himself onto the playoff roster, and John Schreiber, who did not pitch himself into playoff leverage.

And yet through these first three games — two wins over the Red Sox and a loss to the Rays — the Yankees bullpen has allowed one run on two hits and three walks in 8 ²/₃ innings.

David Bednar and Paul Blackburn have remained untouchable. Brent Headrick’s stuff may have taken a step back, but he has still been effective in limited time. Will Warren was helpful against Boston.

And perhaps the most encouraging takeaway from Saturday’s 1-0 loss was Ryan Weathers looking strong in a nine-pitch sixth inning that featured three groundouts to first base.

“Really good to see Weathers come in there and just throw strikes, induce weak contact, have a clean, efficient, short inning,” manager Aaron Boone said Sunday of Weathers, who missed six weeks with a flexor strain and returned as a reliever rather than a starter. “Again, I think he can be massive for us in the postseason.”

After the loss, Weathers said he felt normal, healthy and strong enough that he believed he would be available Monday on one day of rest.

The Yankees could use him not just because he had emerged as the season wore on — posting a 1.29 ERA in his final six starts before the injury — but because Boone has shown less faith in an overworked Headrick. The team’s top lefty all season has only recorded two playoff outs, the second of which came Saturday.

After Blackburn (1 ²/₃ scoreless innings) walked Junior Caminero with two outs in the eighth, Headrick entered to face Liam Hicks and walked him.

With a fastball that averaged 92.6 mph — and had averaged 94.1 mph during the regular season — Headrick induced a hard-hit groundout from Chandler Simpson to escape.

“Pitching absolutely did their job really, really well,” said Boone, who watched the lineup become the biggest problem instead.