On Tuesday night, the Washington Nationals stole seven bases against the Chicago Cubs, with all of them coming against the combination of Jake Arrieta at pitcher and Miguel Montero at catcher. Montero called out his pitching staff after the game, saying the reason the Nationals were able to steal so many bases was because Arrieta was slow to the plate.

But whose fault was it really? While Montero’s words may have been out of line, he did have a point. Arrieta has one of the slowest delivery times among right-handed pitchers this season, averaging 1.71 seconds between his first movement and the ball reaching the catcher in potential stolen base situations. That’s more than a tenth of a second slower than the MLB average for right-handers this year, 1.59 seconds, and is tied for the second-slowest among righties with at least 200 recorded times.

This isn’t a new development for Arrieta—his average delivery time in 2016 was 1.70 seconds, third-slowest among righties with at least 400 times. This has led to basestealers running all over Arrieta, stealing 38 bases on 43 attempts since 2016 for an 88 percent success rate.

Despite Arrieta’s shortcomings, Montero deserves just as much of the blame, if not more. Montero’s average pop time to second base of 2.08 seconds is worst among catchers with at least 10 throws to second base, and it's not even close.

Like Arrieta, Montero didn’t develop this problem overnight. Every year since 2014, Montero has had one of the five slowest pop times to second base among catchers with at least 20 throws. His caught stealing rate has suffered as a result, as he threw out just 5 of 64 potential basestealers in 2016 and 0 of 31 this year.

Looking at those numbers, the Nationals’ baserunning success wasn’t all that surprising. Baseball Info Solutions calculates the likelihood that a stolen base attempt will be successful based on a pitcher’s handedness and delivery time, catcher’s pop time, and runner’s stolen base time. Anthony Rendon, who stole just his fourth base of the season during the game, had a 92 percent chance of being safe on a stolen base attempt against the Arrieta-Montero combination. For comparison, if Wilson Contreras had been behind the plate, Rendon’s projected success rate would have been just 59 percent. On the other hand, if it had been Jon Lester pitching to Montero, that number would have been 71 percent.

Seemingly, both players contributed to the Nationals’ baserunning success on Tuesday. However, Montero was the one who called out his teammate, even though he was just as much at fault for what happened.