A day after Elly De La Cruz jokingly dubbed himself “the fastest man in the world,” the rookie backed it up in the series finale with St. Louis.

De La Cruz flashed his speed, getting two hits, reaching base four times and scoring the go-ahead run with a headfirst slide on an eighth-inning grounder that sparked the Cincinnati Reds over the Cardinals 4-3 on Sunday.

De La Cruz beat out an infield single in the first inning with 31.2 foot per second sprint speed, the 21-year-old getting to the base ahead of 41-year-old pitcher Adam Wainwright.

De La Cruz tied the score 2-2 with an RBI single in the third. He walked in the sixth, stole second and scored on Tyler Stephenson’s single to tie the score 3-3.

Then in the eighth, De La Cruz walked on a full-count offering from Jordan Hicks (1-4) leading off, advanced on Spencer Steer’s ground out and took third on Willson Contreras’ passed ball.

With the infield in, Stephenson hit a two-hopper to Paul DeJong, and the shortstop’s throw was slightly up the first-base line and in the dirt. The ball bounced off Contreras’ mitt as the catcher tried for a swipe tag, and De La Cruz slapped the plate with his left hand.

Ian Gibaut (6-1) allowed one hit in 1 2/3 scoreless innings of relief. Alexis Díaz pitched a 1-2-3 ninth to remain perfect in 15 save chances as the Reds took two of three from the Cardinals.

St. Louis went 1 for 11 with runners in scoring position and is 9 for 70 (.129) in its last 12 games. The last-place Cardinals are 7-15 in one-run games and dropped eight games behind Pittsburgh, the NL Central leader. St. Louis has lost seven of its last nine.