OAKLAND, Calif. -- When he looked back Monday to his time with the Oakland Athletics in 2014, Kansas City Royals right-hander Jason Hammel had bittersweet memories.

Hammel said he loved his three-month stint with the A's after coming to Oakland from the Chicago Cubs on July 5 that season as part of a five-player trade that included right-hander Jeff Samardzija.

But Hammel can't forget his final pitch as an Athletic, in the American League wild-card game against Kansas City at Kauffman Stadium. The game, which Oakland led 7-3 through seven innings, was tied 8-8 in the bottom of the 12th with two outs and Christian Colon on first base when Hammel came on to face Royals catcher Salvador Perez.

Colon stole second base, and Perez grounded a walk-off single down the line to left field, past diving third baseman Josh Donaldson.

"I remember it being a lot of fun and very volatile, just the ups and the downs," Hammel said of the 2014 season. "And then, obviously, the most vivid thing I remember was my catcher that's on the DL now getting a hit off me on the final pitch of the year. That still doesn't sit well with me here. It's disappointing. But that's baseball.

"That was a good group of guys. That was already like the best team in the league, and then you make a couple trades and add on. It was almost like it was supposed to be. We were supposed to win. It hurts that much more because we were so good. It just didn't come to fruition."

Hammel will make his first start at the Oakland Coliseum since 2014 on Tuesday night in the second game of a three-game series against the A's. Oakland will start right-hander Chris Smith. Kansas City won the series opener 6-2 on Monday night, getting a grand slam from rookie catcher Cam Gallagher.

Hammel is 5-9 with a 4.68 ERA in 23 starts overall but has allowed three or fewer runs in 12 of his past 13 starts. During that stretch, he is 4-3 with a 3.73 ERA, 63 strikeouts and 15 walks over 79 2/3 innings.

"What I've always tried to do is be that consistent guy that you know what you're going to get every time out, or you're going to have a good idea, which is a chance to win," Hammel said. "It's almost kind of happened in the same way, just in the broader spectrum, from when I was here. A slow start, made a small adjustment and so far, so good. We're just going to try to keep riding that out.

"We've still got a month and a half of baseball. This is when the fans and the adrenaline kick in and carry us to the promised land, hopefully."

The Royals trail the Cleveland Indians by five games in the American League Central and are a half-game behind the Los Angeles Angels (and tied with Minnesota) for the second AL wild card.

Smith will make his sixth career major league start, all this season at the age of 36 for the A's. In his first three starts, Smith went 0-1 with a 3.32 ERA and a .211 opponents' batting average. In his past three appearances, including one in relief, he is 0-1 with a 7.80 ERA, a .292 opponents' average and six home runs allowed.

Smith gave up five runs on seven hits, including four solo home runs, in a 7-2 loss to Baltimore in his last start Wednesday. Smith, who has a mid-80s fastball and mid-70s off-speed pitches, said it is time to make a few changes.

"That's the big leagues, right, making adjustments," he said.

Smith said all four homers came on four of the handful of pitches he left up. It sounds counterintuitive, but he said he needs to start pitching more in the upper part of the strike zone so that batters won't believe that every ball that "pops up" high is an attackable mistake.

"That's probably one thing that could benefit me as long as I'm here is utilizing the whole zone," Smith said.

Smith has made three career relief appearances against the Royals, allowing no runs on no hits over three innings with four strikeouts and one walk.

Hammel is 4-2 with a 4.40 ERA in five games, including four starts, against the A's. He took the loss against Oakland on April 12 at Kauffman Stadium, allowing four runs on seven hits over 4 2/3 innings in an 8-3 defeat.