Shelby Miller has been a stalwart of the Diamondbacks bullpen, saving Arizona time and time again in the midst of a slew of reliever injuries. Filling in for injured closers Justin Martinez and A.J. Puk, he's been a savior. But not Tuesday night.

On to protect a 4-3 lead in the ninth for a save attempt, Miller gave up back-to-back solo homers, Bo Bichette for the tie and Addison Barger for the win, allowing the Blue Jays to walk off the D-backs 5-4.

Both homers came on splitters, his go-to pitch, especially against left-hand pitchers. Entering today, Miller threw 461 splitters in his career and allowed four total home runs off of them. Today, he threw five of them and got blasted twice.

"That's how unforgiving this game is," said manager Torey Lovullo on Dbacks.TV. "It can turn in a second. Shelby just made a couple of bad pitches and they took advantage of it."

Often criticized for being too slow with the hook, Lovullo lifted starter Brandon Pfaadt after one batter in the top of the sixth holding a 3-2 lead. That might have seemed like a gamble with a usually-porous bullpen. Pfaadt was having anything but a pristine outing however. But he did enough to suppress damage and allow his offense to get back in the game.

Back-to-back doubles by Addison Barger and Vladimir Guerrero Jr. plated a Blue Jays run in the first inning. Guerrero got Pfaadt again with a monster 448-foot homer in the third. Before and after that Pfaadt hit three batters and walked another, but managed to escape those jams.

Pfaadt threw just 81 pitches, 46 for strikes. Unlike his previous handful of starts, Pfaadt only gave up three balls over 100 MPH, including the two from Guerrero. He gave up a leadoff single to George Springer to start that sixth inning, but Kyle Backhus came on to strand the runner, retiring three straight. Pfaadt's final line was 5 IP, 4 H, 2 ER, 1 BB, 3 K as he left the game in line for the win.

The D-backs scored one run in the second, two in the third, and another in the seventh. Three of the runs scored on two-out RBI hits, by Pavin Smith, Josh Naylor, and Geraldo Perdomo. But they also missed a lot of chances to score more, going just 3-for-12 with runners in scoring position and leaving 10 men on base.

Jalen Beeks and Ryan Thompson combined to give up a run in the seventh, allowing Toronto to close to within 4-3. Juan Morillo struck out the side in an impressive eighth inning.

This was the 23rd blown lead in a loss for the D-backs and third time they've been walked off. While the bullpen has looked somewhat better overall of late, it's been very much a two steps forward, one step back process. As they try to cobble together a pen that can allow them to compete and get in position to be buyers at the trade deadline, losses like this sting especially hard.

Arizona falls back to .500 at 36-36 and will lose further ground in the NL Wild Card race. Game two of the series starts Wednesday afternoon at 4:07 p.m. MST. A couple of left-handers will be on the bump, with Eduardo Rodriguez going for Arizona and Eric Lauer getting the ball for Toronto.