Spiegel: Why Arrieta deserves a nod over Lester

Thursday the Cubs won their seventh in a row, their 13th of 14, and sit at 17 games over .500. It's suddenly a 5-game lead for the second wild card, with the Pirates just a game ahead.

Those two teams will likely have a one-game playoff, unless either makes a crazy run at St. Louis.

If they do meet, whether at Wrigley or PNC Park, Jake Arrieta has to pitch.

Jon Lester was very good on Thursday. He struck out 10, went 6 innings and gave up just 2 runs. He has 9 quality starts in his last 11 turns. It was the first time he hasn't gone at least 7 innings since June.

Lester is a proven big-game pitcher. He has the lowest ERA in World Series history for anyone over 20 IP. He has been and can be an ace with a capital A. There are probably 15-20 aces or fewer in the entire league.

His teammate is another one of them.

If it's one game versus the Bucs, the start needs to go to Arrieta.

Lester can take Game 1 of any series, immediately thereafter and beyond. He should go as often as possible. He should pitch whichever enormous game comes up in his spot as October or November may progress, including any must-wins or a Game 7.

But his inability to hold runners is a known weakness you need not expose it in a one-game situation, especially against the fast and aggressive Pirates.

If you didn't watch the third inning against the Milwaukee Brewers on Thursday, then hear it from someone who did.

Lester threw to first base for the first time since April, and made an error that got Jean Segura into scoring position.

Three Brewers runners took enormous, taunting leads. They stared Lester down. Some of them were laughing. It took 5 pitches for Ryan Braun to take the third of 4 steals in the inning, but he could have done so on any pitch he liked.

Jim DeShaies used the word "Yips" in casual mid-inning conversation, because it's silly to pretend this is anything but.

Lester is good at keeping batters off the bases, and remarkable in getting out of the jams he exacerbates. He has to be as good as he is to survive his base runner stress. Even this particular inning only led to one run, on an infield hit in which Lester did not cover first (it may not have mattered).

But it's a matchup-specific risk you need not take. Especially when the option is Arrieta.

Arrieta has registered 10 straight quality starts, going 7-1 with a 1.23 ERA. His ERA in 7 career starts against the Pirates is 2.05, with a WHIP under 1. Also, he's having a better season overall.

The math over Lester's career, and in 2015 particularly, does not support this being a costly long-term problem.

But we're talking about pure distilled randomness. A coin flip game, the smallest sample size to predict. Statistical models alone cannot rule that decision.

Speaking of small samples, there's last year's one gamer from Lester with the Oakland A's, when the Kansas City Royals stole 7 bases and frequently messed with his timing via false starts and taunts.

Pittsburgh is a team capable of taking that same advantage.

Since I had already figured it all out for him, I told Joe Maddon my plan on Tuesday's radio show. He said it will all depend on where the Cubs are in the rotation. That's both a reasonable response, and an effective non-answer.

Who knows; maybe the final few days of 162 will be filled with must wins and everyone will get a chance. The Giants or Nationals could make a run. The Cardinals could somehow fall back.

But if it goes the way it looks right now, it's not that difficult a choice.

• Matt Spiegel co-hosts "The Spiegel & Goff Show" 9 a.m. to 1 p.m. Monday-Friday on WSCR 670-AM. Follow him on Twitter @mattspiegel670.