Showdown weekend: Five big series to watch

We have several big series this weekend between playoff contenders. Let's take a look at those five series and some key things to look for.

Kansas City Royals at Tampa Bay Rays

Status: Rays 2½ behind for second wild card.

Key matchup: Kris Medlen vs. Jake Odorizzi (Saturday). The Royals have a comfortable lead for the American League's best record, but they still have a few things to figure out down the stretch, including Medlen's trying to earn himself a spot in the playoff rotation. Keep an eye on closer Greg Holland as well, who has struggled of late as he's dealt with "general stiffness" in his arm. Manager Ned Yost is in a tough spot: Holland probably needs some rest down the stretch, but he also needs to show he's back to where he was last October.

The Rays, meanwhile, have to scrape together some offense to have a shot at that wild card. Their schedule is pretty tough down the stretch, as they also have two series each against the Blue Jays, Yankees and Orioles.

Baltimore Orioles at Texas Rangers

Status: The Rangers are a half-game up for the second wild card, and the Orioles are 2½ behind.

Key matchup: Kevin Gausman vs. Cole Hamels (Friday). Hamels' first four starts with Texas have drawn mixed results, as he's allowed 14 runs and five home runs in 26⅔ innings. Some of that is just a high batting average on balls in play allowed -- .351 with Texas -- but his strikeout rate is down 5 percent and his walk rate is up just a bit. Is that the result of facing tougher lineups that he faced in the weak National League East or just a small-sample-size blip?

The Orioles have lost seven of eight to blow the lead they had in the wild-card race. They scored more than three runs in just one of those games, but that's what can happen with an offense lives on home runs. Gausman has been pretty solid of late with four starts of at least seven innings in his past six outings and 22 strikeouts and three walks in his past three starts.

Houston Astros at Minnesota Twins

Status: Astros have a five-game lead in the AL West and are neck and neck with Toronto for the league's second-best record; the Twins are a half-game behind the Rangers.

Key matchup: Lance McCullers vs. Ervin Santana (Sunday). On Aug. 9, the Astros' lead in the division was down to a half-game. But then the Angels fell apart, and now Houston has won seven of nine thanks to some phenomenal pitching: The Astros have allowed two runs or fewer in nine consecutive games (the two games they lost were both 1-0 defeats). The Astros are the first team to achieve that since the Pirates in 1992. The last team with 10 such games in a row was the 1974 Orioles. Scott Kazmir looks to help extend that streak on Friday. McCullers-Santana is an interesting battle on Sunday, as the rookie faces the struggling veteran.

After a three-week stint in the minors -- primarily to rest, as he pitched just three innings -- McCullers returned and pitched seven solid innings against the Dodgers (8 H, 2 R, 0 BB, 8 K). The same can't be said for Santana, who has seen his fastball get tattooed to the tune of a .350/.419/.592 line.

Chicago Cubs at Los Angeles Dodgers

Status: The Dodgers hold a 2½-game lead over the Giants. The Cubs are four back of the Pirates in the wild-card standings but a comfortable 5½ up on the Giants for the second wild card.

Key matchup: Jason Hammel vs. Clayton Kershaw (Friday). Congrats, Cubs. A day after facing Madison Bumgarner you get Kershaw, who has been absolutely dominant his past nine starts with seven runs allowed in 70 innings, with 82 strikeouts, seven walks, one home run and a mere .181 average allowed. Did we mention the Cubs lead the majors in strikeouts? The Cubs did beat Kershaw in in June as Kris Bryant and Matt Szczur homered off him. Kershaw also left his past two starts with leads -- only to see the bullpen lose both games. Hammel just ended a stretch of seven starts in which he failed to go six innings.

The Dodgers have struggled against good teams: They're 52-25 against losing teams but just 18-31 against teams that are .500 or better. And after the Cubs series comes the big showdown against the Giants, though they'll have Greinke and Kershaw lined up in that series.

St. Louis Cardinals at San Francisco Giants

Status: The Cards have won five in a row to hold on to a 4½-game lead over the Pirates; the Giants are trying to stay close to the Dodgers.

Key matchup: Michael Wacha vs. Mike Leake (Friday). The Giants are still banged up, minus Hunter Pence and Joe Panik, though Marlon Byrd has done a nice job in six games filling in for Pence. Brandon Crawford also missed Thursday's victory over the Cubs with a tightness in his left oblique, so check to see whether he's back in the lineup, and Gregor Blanco was out with a left hip strain. That pieced-together lineup that included Kelby Tomlinson, Juan Perez and Ehire Adrianza managed to score nine runs.

The Cardinals are battling their own injury issues in the outfield, but Stephen Piscotty has provided a huge lift, hitting .316/.349/.538 with 16 extra-base hits in 126 plate appearances. Matt Carpenter has also found his power stroke, hitting nine home runs in his past 26 games for a .612 slugging percentage after hitting two home runs in 56 games.