The Dodgers- and even Arrieta himself- thought that a hard smash off the glove of second baseman Starlin Castro in the third inning should have been a hit. There's a video on the page linked to in the previous sentence; check it out and see what you think.
While it was a tough chance, I personally thought it was an error. Castro should have come up with it.
In any case, it's one more thrill in an exciting year that came at least a year early. This was the year the Cubs were supposed to simply become respectable; instead, they appear to be headed to the playoffs, albeit as the second wild-card team.
Incidentally, Castro cleared waivers after the game- probably not because of his missed chance. He's having a tough year at the plate and his fielding doesn't show any sign of improving. With Addison Russell having taken over at short and an improved Javy Baez coming up to the parent club after Iowa finished its Pacific Coast League season, the former All-Star became expendable. The Cubs are also reported to be interested in Phillies' second baseman Chase Utley.
Which doesn't necessarily mean that El Jefe is going anywhere- though in would be nice if some American League club would be willing to part with a quality pitcher in exchange for him.