PHILADELPHIA -- If Wednesday night was any indication, Kevin Gausman is postseason-ready -- and so is his devastating splitter. Oh, and so is Vladimir Guerrero Jr.'s bat, not that there was much doubt.

Unfortunately for the Blue Jays, they'll need to work on putting the finishing touches on series before October.

Toronto's bullpen squandered a three-run lead in the eighth en route to a 4-3 loss in 10 innings against the Phillies at Citizens Bank Park. It marked the Blue Jays' fourth consecutive series to end with a loss, including the second straight in which they let a lead of multiple runs in the eighth inning slip away.

“You're taking it one game at a time at this point,” interim manager John Schneider said. “You want to finish off a little mini-sweep here -- two games -- but you can't fault the effort, you can't fault the competitiveness.”

The latest setback cost the Blue Jays a valuable opportunity to further pad their AL Wild Card lead over the rival Rays on the eve of a pivotal four-game series in St. Petersburg. Toronto remains two games ahead of Tampa Bay and 2 1/2 games in front of Seattle for the top AL Wild Card spot.

By Sunday night, the Blue Jays could be anywhere from six games ahead of the Rays to two games behind them.

“The guys know that. They know that every series is important,” Schneider said. “It feels like every series the last three weeks has been pretty magnified. They’re up for it. We’re looking forward to it.”

The good news for the Blue Jays is that Gausman turned in a much-needed bounceback performance, tossing six scoreless innings against the Phillies. He struck out eight and allowed five hits (all singles), while inducing 11 whiffs with his splitter -- his most in any start since July 22.

It was obvious from the start that Gausman had his go-to pitch working. He got Rhys Hoskins and Bryce Harper to each strike out swinging at a splitter in the first inning, then did the same with J.T. Realmuto in the second. Each of the first six outs recorded by Gausman came via the strikeout.

“I came out in attack mode,” Gausman said. “I just felt really good early on.”

But the biggest moment came in the fifth inning when Harper stepped to the plate with the bases loaded and two outs in a scoreless tie. It took Gausman just one pitch -- yes, another splitter -- to get Harper to hit a comebacker that Gausman knocked down and tossed to first to end the threat. Overall, the Phillies went just 1-for-10 with five strikeouts against his splitter while whiffing 50% of the time (11 whiffs on 22 swings).

Though Gausman departed with the game still knotted at zero, the Blue Jays appeared to be on their way to a seventh straight series win after Guerrero hit a towering three-run homer in the eighth. The go-ahead blast -- which left his bat at 110.6 mph and traveled a projected 429 feet -- extended his hitting streak to 14 games, during which he’s hitting .306 with eight extra-base hits.

The lead would prove to be short-lived.

Yimi Garcia served up a leadoff homer to Realmuto in the bottom of the frame, then -- after recording a pair of outs -- allowed three straight singles before handing the ball over to closer Jordan Romano with runners on the corners and two outs in a one-run game. Kyle Schwarber welcomed him with a game-tying single, setting the stage for Matt Vierling’s walk-off single off Adam Cimber in the bottom of the 10th.

“Obviously, a rough way to end the night, but I thought we battled the same way we have the last couple nights -- and really, the last week,” Gausman said. “We’ve been playing exceptional baseball. It’s unfortunate the way we lost, but we just continue to play good baseball at an important time of the season.”

The next week figures to carry even more significance as far as determining how the Blue Jays’ postseason path might shake out. Following their four-game set against the Rays, the Blue Jays return home to host the first-place Yankees.

“These games are a preview of what's to come hopefully,” Schneider said of Wednesday’s back-and-forth loss.

Before quickly adding with a smile: “Just with a different outcome.”