NEW YORK -- From a performance standpoint, the Yankees feel top pitching prospect Justus Sheffield isn't quite a finished product, but he's close.

Mentally? He's ready the major leagues, close friend and veteran starter CC Sabathia said.

"One-thousand percent," Sabathia said before Sunday's rainout of a game against the Mets at Yankee Stadium.

If Sheffield's consistency can catch up, he could give a huge second-half boost to the Yankees, who are looking to trade for starting pitching and could arguably use bullpen help.

At Triple-A Scranton/Wilkes-Barre, Sheffield, a lefty, is is 3-3 with a 2.44 ERA in 12 games (11 starts) at Triple-A Scranton/Wilkes-Barre. On Saturday, he gave up one run in 5 2/3 innings, striking out four and walking one.

Manager Aaron Boone said Sheffield "absolutely" could help the Yankees -- and soon.

"He's had another really good year," Boone said. "He's putting himself in position, probably in the short term, to be in consideration for a spot, whether it be a rotation need, whether we have a bullpen need. He certainly probably knocking on that door and being a guy a lot closer to being an option."

Recently, Yankees Vice President of Baseball Operations Tim Naehring said there's a "plan in place" for the Indians' 2014 first-round pick but that it was just "a matter of stringing innings together that would warrant a call-up.

That didn't surprise Sabathia, who quickly became close with Sheffield after the Yankees acquired him in a package alongside outfielder Clint Frazier in a deal that sent elite reliever Andrew Miller to Cleveland at the 2016 trade deadline.

Sabathia, 38, and Sheffield, 22, keep in touch via text during the season. When he can, Sabathia said, he checks Sheffield's stats and watches video of his outings via an application Yankees coaches use to track minor leaguers.

Sabathia said Sheffield's wiser-than-his-years mindset was "what attracted me to him."

Sabathia said when it comes to Sheffield, it was "the way he went about his business and carried himself" that was so impressive.

"He wants to be good," Sabathia added. "He asks a lot of questions. Obviously, the stuff is there. He's got the stuff to pitch in the big leagues. Wanting to be better and asking questions and just trying to be around the right people, I think, is something he does a good job of."

What kinds of questions does Sheffield ask Sabathia?

"Just things about pitching, about pitching (to) certain guys, certain sequences and things like that that," Sabathia said. "You can always tell through a young guy's questions how mature he is, for sure."

In spring training, Sheffield had a rough time, giving up seven earned runs in 5 1/3 innings over three outings.

Still, Sabathia said, "his stuff is electric."

"It's there," Sabathia said. "I know everybody was a little down about his spring training, but for me it was different. He's got this stuff. He's right there. He just got a little too excited in those second innings. In those first innings in the spring training outings, he was lights out. Then he would come out trying to strike out the side or be really impressive and end up leaving the ball down the middle or walking some guys, stuff like that. I think that just comes with getting out there and being mature and not trying to do too much."

Naehring pointed to the way the Rays brought David Price up via the bullpen in 2008. Sabathia said he believed Sheffield could handle that, if necessary.

"You can put guys in a situation where they have a chance to win, and they'll always show up," Sabathia said. "I think he'll be fine, if that's the route that it went, if he has to come through the bullpen to crack in, I think he'd be fine at it."

Brendan Kuty may be reached at bkuty@njadvancemedia.com. Follow him on Twitter @BrendanKutyNJ. Find NJ.com Yankees on Facebook.