There has always been talk about how the Rangers struggle against soft-tossing lefties (there are other variations that I'll try to touch on, too), and at this point, it's hard to separate genuine concern about their ability to do so from people just playing into a running joke. Literally every team's fans say the same thing. Confirmation bias just makes you remember the times those oh-so-hittable guys shut their team down. However, because I was bored, I decided to see if the Rangers have actually struggled against such pitchers in recent history (this will be a very surface-level analysis. I don't have a lot of time to dig too deep right now).
To start, I used baseball-reference's Play Index to get a list of every game a left-handed pitcher has started against the Rangers: HERE'S THE LIST.
First, I found that the sample's ERA is 5.25, and their R/9 against them is 5.9 Over the past two years, the Rangers have averaged 5.13 R/G. So, on that level, they definitely score more off lefties.
However, the saying isn't just lefties in general. It's soft-tossing lefties, right?
So I manually deleted anybody that had an average fastball velocity greater than or equal to 90.0 mph (checked against FanGraphs' velocity over the last two years).
After this, it was populated with only 29 starts: MOST OF THEM WERE JASON VARGAS.
ERA drops down to 4.96, but R/9 drops to 5.8. I don't have a ton to say about this right now, because I have to go eat. I'll just present the data and let you discuss it if you wish.