NEW YORK -- The Arizona Diamondbacks will get a boost Thursday afternoon they would have had a hard time seeing 27 days ago.

Diamondbacks left-hander Robbie Ray will complete his swift return from a scary head injury Thursday when he is activated from the disabled list before taking the mound in the finale of a four-game series against the New York Mets at Citi Field.

Ray (9-5, 3.11 ERA) is scheduled to oppose Mets right-hander Rafael Montero (2-8, 5.47). New York will be trying to salvage a split of the series after a 4-2 win Wednesday night.

The victory was just the second in the last 10 games for New York (55-70). Arizona (69-58) remained a half-game ahead of the Colorado Rockies in the race for the National League's first wild card.

The outing will be the first on a major league mound for Ray since July 28, when he threw 1 2/3 scoreless innings before he was hit in the head by a 108 mph line drive off the bat of St. Louis Cardinals first baseman Luke Volt. Ray never lost consciousness but was diagnosed with a concussion and needed three staples to close a cut on the side of his head.

He was placed on the seven-day concussion disabled list July 29 and was able to resume throwing within a matter of days. Ray struck out 11 batters in 4 2/3 innings in a rehab start for Class A Visalia on Aug. 17.

Ray's quick comeback is likely to serve as a dual inspiration to his teammates, who are getting back a pitcher who received his first All-Star Game berth this year and entered Wednesday ranked ninth in the National League in strikeouts (151).

"It's good to have Robbie back; we are getting an All-Star pitcher that's carried us at times," Diamondbacks manager Torey Lovullo said after Wednesday's game. "We are excited because it's him and then we are excited because it means that he's healthy and he's taken the journey and come out on the other side of this thing. We are really thrilled for him."

Ray threw 80 pitches in his rehab start, which Lovullo said will put him in line to throw 90 to 95 pitches on Thursday.

Montero will be looking to win consecutive starts for the first time as a big-leaguer. He claimed the victory last Saturday after allowing one run in six innings as the Mets beat the Miami Marlins 8-1.

While Montero entered Wednesday with the 14th-highest ERA in baseball (minimum 75 innings pitched), he has performed better lately. He has given up three runs in 12 innings in his last two starts and has a 4.53 ERA while striking out 59 and walking 23 in 57 2/3 innings since he was promoted from Triple-A Las Vegas on June 14.

Montero had an 8.24 ERA, 20 strikeouts and 17 walks in his first 19 2/3 innings for the Mets this season.

Montero's command was one of his strengths in the minors and manager Terry Collins said he's beginning to figure out his stuff is good enough to attack hitters in the majors.

"I think it happens a lot, until you really find out that you can trust your stuff, that you can get outs," Collins said. "Raffy's a perfect example. All of a sudden, he realizes, 'Hey, look, I can throw a ball and not have to worry, because I know I can come back and make a better pitch.'"

Ray is 1-0 with a 0.53 ERA in three career starts against the Mets. Montero is 0-1 with a 3.00 ERA in two career appearances (one start) against the Diamondbacks.