Defending champions in the National Leagues Central, the Reds were on the fringes of contention in the division at the All-Star break along with Milwaukee, St. Louis and Pittsburgh.
Since, they've won two of three from St. Louis, lost two of three to Pittsburgh, won two of three from Atlanta, dropped four straight to the New York Mets, swept three from San Francisco, lost two of three to Houston and the Chicago Cubs and won two of three from Colorado.
They won a second straight against the Padres on Saturday after combining for seven home runs in a 13-1 rout.
Cincinnati has won four straight, but trails first-place Milwaukee by 10 games and is five back of second-place St. Louis.
Homer Bailey (7-5) earned the win after giving up one run and scattering six hits over seven innings.
Kyle Blanks accounted for the lone Padres run with a solo homer in the fourth.
Tim Stauffer (7-9) was pegged with the loss after giving up nine runs on seven hits -- including five home runs -- in just three innings.
Southpaw Dontrelle Willis gets his seventh crack at a first win in a Reds uniform when he starts the finale.
He debuted with Cincinnati on July 10 at Milwaukee and has gone 0-2 in six starts in spite of allowing three runs or less in each start while pitching at least six innings five times.
The Reds are 2-4 in his outings and Willis is 2-1 in five lifetime starts against San Diego.
For the Padres, lefty Wade LeBlanc gets his sixth start of the season and second of his career against Cincinnati.
Now 27 after celebrating a birthday last week, the Louisiana native allowed six runs over 12 2/3 innings while losing his first two decisions, and has subsequently gotten no-decisions in three outings.
San Diego is 1-4 in his starts and has been outscored, 31-21.
He's 0-1 in three road starts in 2011 with a 5.27 earned run average across 13 2/3 innings.
Cincinnati took two of three from the Padres earlier in the year.