With the Rays becoming the first team to play 81 games as of the end of Sunday’s action, we’re almost at the exact midpoint of the 2023 MLB regular season. Though anything can happen in the second half, we have enough of a sample size to gauge who MLB’s likely contenders are.

Several of those contenders, including the Rays themselves, will be put to the test in high-profile matchups this week. Tampa Bay will face Arizona in a battle of division leaders, while a couple of  major intra-division showdowns could have playoff implications.

Those matchups, and more, are included in our five series to watch during the week of June 26:

Reds (41-37) at Orioles (47-29)
3 games (Monday-Wednesday)

Head to head: These teams last played in July 2022, when the Reds took two of three games in Cincinnati.

Storyline: These cities don’t share the same rivalry in baseball that they do in football, where the Cincinnati Bengals eliminated the Baltimore Ravens in the most recent playoffs. But what the baseball teams do have in common with one another is young rosters that are vastly outperforming preseason expectations. The Reds have their highest win percentage since 2013, while the Orioles have their highest since 1979.

Watch out for: Elly De La Cruz. What will the rookie phenom do next? Whether it’s hitting for the cycle, setting speed records on the basepaths, or breaking Statcast with absurd exit velocities, the only constant in De La Cruz’s game is that it’s always worth watching.

Giants (44-34) at Blue Jays (43-36)
3 games (Tuesday-Thursday)

Head to head: These teams have not faced off since 2019, when the Giants won two games in Toronto and split a two-game set in San Francisco.

Storyline: Are the Giants for real? San Francisco entered June at exactly .500, at least five games back of both the Dodgers and Diamondbacks in the NL West race. But the Giants have turned it around since then, going 16-6 in June as they passed the Dodgers and now sit only 2.5 games back of Arizona.

Watch out for: Vladimir Guerrero Jr. The fifth-year star continues to be a Statcast darling, as his 137 hard-hit balls (95-plus mph exit velocity) rank second in MLB behind only Ronald Acuña Jr.(147). In two career games against the Giants (both in May 2019), Guerrero has five RBIs, a 1.841 OPS and two homers -- the first two homers of his MLB career.

Rays (54-27) at D-backs (47-32)
3 games (Tuesday-Thursday)

Head to head: These teams last played in May 2019, when the Rays won two of three games at home.

Storyline: Two division leaders go at it. For the Rays, who have made each of the past four postseasons (including two AL East titles in that span), their 2023 success was somewhat expected. But Arizona is among MLB’s more surprising division leaders, as the D-backs and Rangers (more on them later) are on pace to become the first teams ever to win a division one year after finishing 35 or more games out.

Watch out for: Corbin Carroll. Carroll was still in high school the last time these two teams played, but he’s since become the face of Arizona’s turnaround. Via FanGraphs, he ranked second in MLB in offensive WAR behind Acuña entering June 25, giving him an outside shot to be the first rookie to win MVP since Ichiro Suzuki in 2001.

Marlins (45-34) at Braves (50-27)
3 games (Friday-Sunday)

Head to head: The Braves are 6-1 against the Marlins this season. That represents both Atlanta’s most wins against any opponent in 2023, and Miami’s most losses to any opponent in 2023.

Storyline: Can the Marlins make the NL East race competitive? Miami has surged into the playoff conversation by winning 20 of its past 28 games, though there are signs that their success may not be that sustainable (such as their 19-5 record in one-run games, the best record by any team in such games in the Modern Era). Still, as it stands now, the Marlins are in the best position of any team seeking to end Atlanta’s run of five straight NL East titles. 

Watch out for: Eury Pérez. Here’s some context for the remarkable run that the rookie is on: He is the only pitcher to allow one or fewer runs in a six-game span in a single season (min. 30 IP) at age 20 or younger since at least 1901. On Saturday, he will be put to the test like never before against a loaded Braves lineup featuring the likes of Acuña, Matt Olson, Sean Murphy and more.

Astros (42-36) at Rangers (47-30)
4 games (Friday-Monday)

Head to head: The Rangers took two of three games in Houston in April. In 2022, the Astros went 14-5 against the Rangers, which represented their most wins against any opponent in their World Series-winning season.

Storyline: Is this the year the torch gets passed? From 2017-22, the Astros made six consecutive ALCS (the all-time AL record), while the Rangers had six consecutive losing seasons. But thus far in 2023, it’s the Rangers, led by first-year manager Bruce Bochy, who lead MLB in run differential and lead the Astros in the AL West.

Watch out for: Adolis García. You need to score runs to win games, and García is one of four players to knock in at least 60 of them this season (also Olson, Rafael Devers and Shohei Ohtani). This includes three RBIs in the Rangers’ series win over Houston in April. Led by García, Texas’ 5.95 runs per game is the highest total by any team since the 2007 Yankees (5.98).