The Mets acquired Lockett and second baseman Sam Haggerty from the Cleveland Indians in exchange for catcher Kevin Plawecki during the offseason. Lockett, 25, appeared in four games (three starts) with the San Diego Padres in 2018, going 0-3 with a 9.60 ERA in 15 innings.
Now, Lockett will seek his first big-league victory as a fill-in for Mets ace Noah Syndergaard, who is on the injured list due to a strained right hamstring.
"He's been throwing the ball over the plate," Mets manager Mickey Callaway told reporters when asked about Lockett, who has four walks in 31 2/3 innings this season in the minors. "He's healthy. He's the guy that we brought into the organization this offseason to be that sixth starter, that depth starter that we knew we'd need at some point.
"(Thursday) is going to be his opportunity to show what he can do."
The Mets hope a fresh face can help turn around a subpar stretch that has included six losses in the past nine games.
The Cubs will turn to veteran right-hander Tyler Chatwood, who will make only his second start of the season and his first since he threw six shutout innings April 21 against the Arizona Diamondbacks.
Chatwood (3-1, 3.60 ERA) joined the Cubs before the start of last season on a three-year, $38 million deal, but injuries and inconsistency pushed him into a long-relief role for much of the past year.
On Thursday, he will take the place of right-hander Kyle Hendricks, who was placed on the injured list because of soreness in his pitching shoulder.
"He's been pitching a lot better," Cubs manager Joe Maddon told reporters about Chatwood. "He came here for a specific reason. We believe he's earned this opportunity to pitch in this situation."
Chatwood, asked about getting another opportunity to start, said, "It's gratifying. I feel like I've thrown the ball pretty well. I feel fresh. I think I'm in a better spot than I was last time (starting in late April), and I threw 70-something pitches last time."
In eight career starts against the Mets, Chatwood is 3-2 with a 4.17 ERA. He has walked 25 and struck out 22 in 41 innings.
Cubs catcher Willson Contreras is coming off a two-homer, five-RBI performance in a 7-3 win over the Chicago White Sox on Wednesday night. Contreras has 15 home runs in 63 games this season after hitting 10 home runs in 138 games in 2018.
The Mets hope Lockett will be ready for Contreras and all of the Cubs' sluggers.
Lockett missed the first six weeks of the season because of a right arm injury before reporting to the minors, where he went 1-1 with a 3.69 in six games (five starts) with Class-A St. Lucie and Triple-A Syracuse.
He faced the Cubs once last year, and he allowed five runs on nine hits in five innings at Wrigley Field.
"The good part is he's pitched in the major leagues before," Callaway told reporters. "He's not going to be making his debut. And you know what? When that's who you call up, you've got to get the job done no matter what the circumstances are. It's never easy. We always understand that. And we expect him to go out there and pitch like he did in Triple-A."