Welcome to the National League notebook, a weekly look at players, topics and trends around the Senior Circuit. This week we check in on the mystifying Cardinals, the torrid Anthony Rendon, the thunderous Josh Bell and the wild Wild Card race.

It has been a brutal month for the Cardinals. There’s no getting around that. After an April filled with optimism, a 7-18 May has frustration soaring in St. Louis. (Thank goodness for the Blues!)

It hasn’t just been rough, though -- it’s been weird. By some measures, Cardinals starters -- understandably a primary target of fan discontent -- have actually pitched pretty well, and their relievers even better. And in all but one critical department, their hitters are doing their jobs.

Again, it’s weird.

By conventional measures, yes, the pitching has struggled. Cardinals starters are 12th in the NL in both innings and in ERA. By FIP, a defense-independent pitching measure, it’s even worse -- 13th, at 4.88. But when you look at xFIP, another defense-independent measure, they’re a perfectly respectable seventh. It’s a similar story for the relievers -- sixth in ERA, eighth in FIP, fourth in xFIP.

So what, exactly, does that mean? Mostly, it seems to mean they’re having really bad home run luck. Yes, home run luck.

FIP takes a pitcher’s strikeouts, walks and home runs, and extrapolates what his ERA should be. xFIP goes one step further, projecting what the pitcher’s home run rate should be based on an average home run-to-fly ball ratio. So, based on actual home runs, the Cardinals have struggled. Based on the homers they should have given up, it looks a lot better.

That’s not very satisfying when they’re actual home runs that count, but it might be encouraging going forward.

Oh, and one other strange thing. If you’re wondering whether this has to do with the ballparks they’ve played in, or the weather, or some external factor like that, it seems unlikely. That’s because the reverse has been true for Cardinals hitters.

According to Statcast, Cardinals pitchers have the second-largest gap in baseball between expected slugging, based on quality of contact, and the actual slugging they’ve allowed. Their hitters? The second-largest gap in the OPPOSITE direction. Only one team has gotten less to show, power-wise, for the quality of contact it’s made this year.

It seems very likely that at least one of these, if not both, will normalize before long. And as you’ll see below, there’s still plenty of opportunity in the NL postseason race. It’s early, and baseball is weird.

Player of the week

It’s probably not quite accurate to call Anthony Rendon the most underrated player in baseball, but he may be the least heralded truly great player in the game. As good as he’s been in the past, he’s better this year. And as good as he’s been this year, he’s been better over the past two weeks.

Rendon dealt with an elbow injury in late April that landed him on the injured list, and he scuffled just a bit in his first week back. Since then he’s crushing.

Over Rendon’s last 16 games, going back to May 14, he has a .345/.472/.724 line. He has 14 walks against just eight strikeouts, and 12 extra-base hits in 58 at-bats. He’s basically hitting like Barry Bonds in 1993.

Oh, and he’s a free agent after the season.

Stat of the week

It’s no secret that Josh Bell is having a great year. You might not have known this, though. Bell’s home run on Wednesday was his 18th of the year, but maybe more notably, his double on Thursday gave him 40 extra-base hits on the season. That’s six more than Cody Bellinger, who himself has three more than any other hitter in the Majors.

Put another way: It’s the most extra-base hits before the end of May for any Major Leaguer in more than 20 years. The last player with 40 or more XBH before June 1? Edgar Martinez, who in 1996 had 43 for the Mariners at the end of May. The last player even to get to 39 was Lance Berkman, for the 2008 Astros.

Race of the week

You won’t find many teams that will admit they’re thinking about the Wild Card at the end of May. That’s fine. They don’t have to. We can.

The NL Wild Card race is shaping up to be absolutely bonkers. We’re likely to have good division races in the East and Central as well, but the Wild Card? That could be a battle royal. With the Rockies surging, the Mets on the rise and the Cardinals flagging, this race is a mess. That’s a compliment.

Milwaukee and Atlanta lead. The Cubs are only a game ahead of the Brewers in the Central, so they’re part of this mix as well. Five teams are within 2 1/2 games of the Braves. And at least two more, the Reds and the Nats, are still in the picture.

Looking ahead: Series of the week

After those red-hot Rox finish a long homestand this weekend against the Blue Jays, the degree of difficulty ratchets up a bit. Fifteen of their ensuing 22 games are away from Denver, and the trip starts with a doozy -- three games against the Cubs at Wrigley Field on Monday, Tuesday and Wednesday.