The one big flaw this manga suffers from... is the romance.

As a sportsmanga it is pretty straight forward and cool. The author doesn't waste any time explaining the rules of the game and throws you right into it. It might be a tad intimidating if you never followed a baseball game before, but slowly you'll get accustomed to the positions and terms of the game. Which I actually enjoyed about Natsuzora and Run. The artstyle is dynamic in game scenes and those games can become really tense.
Another enjoyable thing is the MC: Chiaki is not bad at baseball, but he's also no prodigy. He's just a passionate guy living for the game. So there's a lot more leeway for the story and games to develop, instead of having everything depend on one single player. Which this manga manages in a lovely manner: It is all about the team. Even the sidecharacters have their own quirks and add something to the team.

So yes, as a sports manga Natsuzora and Run can be recommended. As a romance manga... well...

This might get a teeny tiny bit *spoilery*, so read at your own risk.

The "romance" takes up quite a big chunk of the story. But calling it "romance" might be exagerrated, because all there is, is a constant back and forth between the MC and the other person in question. The status quo shifts every other chapter into one of the two directions, and it feels like a bit of a waste having this nonsense going on for so long. There's not much to gain from it in terms of character development - it's more or less just there.

Yet, I still recommend Natsuzora and Run, and if it's just for the baseball action. The rest *can* be tolerated, since there's some lovely sidecharacters making up for that.