The Reds have won 13 of 14 to establish baseball's best record as they host the team chasing them in the NL Central - the wild card-leading Pirates - on Friday night.
Cincinnati (64-41) and Pittsburgh (60-44) could both be headed to the postseason for the first time since the Reds eliminated the Pirates in six games in the 1990 NLCS en route to their last World Series title.
Pittsburgh has won 11 of 16 since July 16, but Cincinnati has taken 14 of 17 in that same span - all without injured star Joey Votto - to build a 3 1/2-game lead in the division.
The Reds took three of four at home from San Diego capped by Thursday's 9-4 victory. Todd Frazier homered in a six-run second inning and finished with three RBIs.
The Pirates are 5-4 against the Reds this year. These teams haven't met since early June, and Pittsburgh is eager for the chance to gain ground.
The Reds have fared well against Andrew McCutchen, whose .231 average in the season series is his second-worst against an NL club. McCutchen raised his major league-best average to .373 by going 6 for 11 with three walks this week as the Pirates took two of three on the road from the Cubs.
The Pittsburgh star is 0 for 1 with two walks against Mat Latos (9-3, 4.17 ERA), who is 3-0 with a 2.16 ERA in four career starts against the Pirates. Latos struck out 11 over six innings May 6 in a 5-0 victory in his lone start versus Pittsburgh this year.
The right-hander won his second straight outing Sunday by allowing two runs over eight innings in a 7-2 victory at Colorado.
Latos will be opposed by Wandy Rodriguez (7-9, 3.82), who will make his second start for the Pirates since being acquired last week from Houston. Rodriguez faced his former team in his first outing, giving up three runs with a season-high five walks over six innings Saturday as he did not get a decision in a 4-3 victory.
The left-hander is 1-1 with a 6.35 ERA in three starts against the Reds this year with the Astros.
The Reds' 9-4 victory over the San Diego Padres on Thursday means the Reds will be in first place in the National League Central no matter what happens in the upcoming three-game series with the Pittsburgh.
That doesn't make the series any less important.
"I think it's good for both of us," right fielder Jay Bruce said. "Those guys are as relevant as you can be. They're not going anywhere. We're going to have to play good baseball. We've been doing great. We're just going to have to play the way we've been playing.
"I think we believe we're the better team. I think they believe they're the better team. That's why we play."
The Reds have won three consecutive games, 13 of the last 14 and 20 of the last 23. However, the Pirates are only 3 1/2 games back in the Central.
The Reds have scored 43 runs in the last six games.
"Things are going well right now," catcher Ryan Hanigan said. "Guys are playing loose, taking real aggressive swings in the zone. Nothing surprises me right now. We've got some momentum. We expect to score runs. We expect to get outs.
"We're having fun. Things are rolling. There's a long way to go, but we're in good spot."
RHP Johnny Cueto pitched 7 1/3 innings against San Diego, allowing four runs on eight hits. He walked one and struck out nine. He threw 103 pitches, 74 of which were strikes. Cueto's outing gave the bullpen a much-needed break going to the series with Pittsburgh. "Johnny pitched well," catcher Ryan Hanigan said. "He wasn't as dominant as he can be obviously. He left his breaking ball up a couple of times and it got hit. He knows that. For the most part, he managed the game."
1B/3B Todd Frazier went 1-for-4 with a home run and three RBI. He has home runs in back-to-back games and in three of the last five games.
INF/OF Wilson Valdez's stiff neck was improved Thursday. "But not much," manager Dusty Baker said. "If anybody ever had a bad neck from sleeping, it don't get better (quickly). … He'd have a better chance if we had a night game tonight, versus day after night. It hurts when you get jarred. It's goes all up and down your vertebrae."
2B Brandon Phillips missed his second consecutive game because of a strained left calf. The plan for Phillips was not to play him until at least the Pittsburgh series that starts Friday.
1B Joey Votto will not be activated for the Pittsburgh series. Votto took groundballs at first base on the field Thursday. He also hit in the cages. He's yet to hit on the field. It's been 16 days since he had arthroscopic surgery on his left knee.
RHP Nick Masset moved his rehab assignment to Class A Dayton on Thursday, and he threw a scoreless inning. Masset, sidelined all season due to a right shoulder injury, had thrown two scoreless innings last week in the rookie-level Arizona League.
By The Numbers: 80—That's the number of innings RHP Johnny Cueto had gone without allowing a home run before Eddy Rodriguez took him deep in the third inning Thursday.
Quote To Note: "The problem is I've had a couple in the past. It's not that this one was overly bad. It was just you want to be careful and not get banged up again." —C Devin Mesoraco, on going on the seven-day disabled list because of a concussion.