OAKLAND, Calif. — Ivan Nova says you can expect him to be better in the second half of his first and likely only season in the White Sox’ rotation.

The Sox can only hope. After posting remarkably consistent ERAs of 4.17, 4.14 and 4.19 in his last three seasons with the Yankees and Pirates, Nova takes the majors’ third-worst ERA among qualifying starters, 5.58, into his outing Friday night against the Athletics at the Coliseum.

But Nova has a 3.98 ERA in his last nine starts, including 5‰ innings of one-run ball against the Cubs in his last outing.

“I’ve been pitching a lot better,” Nova said. “I know at the end, the numbers are going to be there. What do we have, three months left? That’s a lot of baseball.”

Nova, 32, becomes a free agent after the season and, with his track record with the Yankees and Pirates, could attract interest before the July 31 trade deadline if he strings together a few good starts.

Rest assured, Nova said his bad start had nothing to do with health. His mother, for one, needed that assurance, he said.

“One thing my mother always asks, ‘Are you hurt?’ And I tell my mother, ‘How many times have you seen me go through this?’ ” Nova said. “And she says, ‘A lot.’ And I say, ‘Was I hurt? No.’ That’s part of the game. Ten years, I’ve been through a lot.

“I feel 100 percent. Stronger than ever, super-strong. Sometimes the results don’t show it, but it’s going to change.”

Castillo is closer

Catcher Welington Castillo’s minor-league rehab assignment shifted from Class AA Birmingham to Class AAA Charlotte. If Castillo (oblique strain) returns, a decision would likely be needed on Zack Collins, who has caught only 28 innings and made 27 plate appearances (he’s 1-for-22) while taking notes from James McCann since being called up almost three weeks ago.

The addition of left-handed-hitting, waiver-claimed first baseman AJ Reed would take DH at-bats from Collins, who might be better served getting regular swings again with Charlotte.

TV ratings highest in five years

The Sox’ ratings on NBC Sports Chicago are the highest they’ve been at the All-Star break since 2014. Sox games are averaging a 1.18 household rating in the Chicago market, up 36 percent from last season at the break. Five years ago, they averaged a 1.38. In June, the Sox averaged a 1.57 on NBCSCH, which was the team’s highest-rated June since 2012 (2.26) and its highest-rated month since April 2014 (1.68).

This and that

Since April 26, Mike Fiers, the Athletics’ starter Friday, owns a 2.52 ERA, fourth-best in the American League. He’s 2-0 with a 2.21 ERA in six career starts against the Sox.

Andy Masur is filling in for vacationing analyst Darrin Jackson on the Sox’ radio broadcasts from Oakland.