Having completed a four-game sweep that knocked the Pittsburgh Pirates out of first place in the National League Central, the Phillies will step up in class when they begin a three-game series against the Arizona Diamondbacks on Tuesday night at Citizens Bank Park. The Diamondbacks are the Phillies' first opponent this season that made the playoffs last season, but more than that, the Snakes come to town with the best record in the National League, 15-6.

The Diamondbacks, led by slugger Paul Goldschmidt, had one of the best offensive teams in the majors last season, but so far this year, their pitching staff is carrying them. They are hitting just .225 and are in the middle of the pack with 95 runs scored, but their pitching staff's 2.75 ERA is tied for third in the majors and the best in the National League. The Philies are second in the league with a 3.01 ERA.

Zack Greinke (2-1, 4.13 ERA) is the biggest name among the Arizona starters, and Jake Arrieta (2-0, 2.04) will face him Wednesday night. Arizona's best starter has been lefty Patrick Corbin (4-0, 1.89), but the Phillies will not have to face him. They will face Robbie Ray (2-0, 4.98) Tuesday night and Matt Koch (0-0, 1.13 in one start and one relief appearance) Thursday. Vince Velasquez (1-2, 3.80) will pitch for the Phillies on Tuesday and Ben Lively (0-1, 4.64) will pitch on Thursday.  The Diamondbacks' greatest strength has been their bullpen, which has a major-league-best 1.88 ERA and has converted all eight of the team's save opportunities. Diamondbacks manager Torey Lovullo, whose big-league career ended with the Phillies in 1999, has used nine relievers this season, and none has an ERA higher than 3.00.

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—  Bob Brookover  (extrainnings@philly.com)

Arizona’s Zack Greinke will face the Phillies’ Jake Arrieta in a premier pitching matchup Wednesday night.
Arizona’s Zack Greinke will face the Phillies’ Jake Arrieta in a premier pitching matchup Wednesday night.

Maikel Franco watch

We knew when the Phillies decided to sign Scott Kingery to a six-year deal and keep him on the opening-day roster that the rookie was going to cut into the playing time of some of the regulars. We now also know that the greatest impact has been on third baseman Maikel Franco. Kingery has made six starts at third base this season, and five of them have come when the Phillies were facing righthanded pitchers.

With the Phillies facing a lefty in Robbie Ray on Tuesday night, Franco figures to be back in the lineup. Franco has started all five times the Phillies have faced a lefty this season and has done quite well against them, hitting .400 with two home runs and 13 RBIs in those five games. In his 10 starts against righthanders, Franco is hitting just .158 with a .233 on-base percentage. Given that knowledge and the fact he is 1 for 10 in his career against Arizona's scheduled Wednesday night starter, Zack Greinke, it would not be surprising to see Franco back on the bench for the second game of the series.

Here's the thing: Franco's career does not show any significant distinction between his splits against righthanders and lefthanders. Last year, in fact, he was better against righthanders. He has a .236 career average and a .745 OPS against lefthanders and a .719 OPS against righthanders. If I had to place a bet, however, I'd guess that Kingery will continue to get significant time at third base when the Phillies face tough righthanders, especially ones with nasty breaking balls.

The rundown

Jake Arrieta, the Phillies' prized free-agent addition during spring training, takes his role as a mentor to the younger starters seriously, and he has helped the trio of Nick Pivetta, Vince Velasquez and Ben Lively. But Arrieta told our Scott Lauber that he also has been energized by watching his young teammates pitch. He is especially motivated by watching the work of Aaron Nola.

Important dates

Today: Vince Velasquez vs. Robbie Ray, 7:05 p.m.
Tomorrow: Jake Arrieta vs. Zack Greinke, 7:05 p.m.
Thursday: You can watch the 1:05 p.m. game only on Facebook
Friday: Phillies open a three-game series vs. Atlanta, 7:05 p.m.

Phillies catcher Jorge Alfaro breaks his bat after striking out in Atlanta. He is one of four Phillies to strike out 21 times this season.
Phillies catcher Jorge Alfaro breaks his bat after striking out in Atlanta. He is one of four Phillies to strike out 21 times this season.

Stat of the day

The Diamondbacks were hopeful that third baseman Jake Lamb would be back for the start of the series against the Phillies, but elbow inflammation will extend his time on the disabled list. Lamb has not played since April 2 because of a shoulder injury. He has been a Phillies killer over the years. In 17 career games against the Phillies, he has a .344 average with five home runs, 14 RBIs and a 1.114 OPS. The lefthanded-hitting third baseman is also batting .400 (10 for 25) against the Phillies' three schedule starters in this series. Devin Marrero, Lamb's primary replacement at third base, is hitting .219 with one extra-base hit.

From the mailbag

Hi Bob. Can you help me understand the Phillies' high strikeout rate this year? The K-K-K-K train keeps rolling.  The team struck out 12 times Sunday vs. only 8 hits and 3 runs. On Saturday, it was 10 Ks vs. 7 hits and 6 runs. On Friday, it was only 5 Ks vs. 8 hits and 2 runs. My tally shows 161 hits so far thru Sunday vs. 211 whiffs, or about 30% more Ks than hits.  Is this disparity normal?  We're striking out at over a .300 rate, which seems abnormally high. Sure we swept the Pirates, but the Ks are like a leak in a bucket; sooner or later, the water is gone.

Ken C.

Answer: There's no question, Ken, that the Phillies are striking out a lot. They have whiffed on 30 percent of their at-bats this season. Only San Diego, at 30.2 percent, has struck out at a higher rate. The Phillies, however, are doing other things so well that it is helping them compensate for that strikeout rate. They are, for instance, drawing 4.7 walks per game, the best rate in baseball, which is why they have a .325 on-base percentage, which ranks sixth in the National League despite a .230 batting average that is 10th in the league. The Phillies also lead the majors in pitches seen per at-bat and are third in the National League at five runs per game. The Phillies' approach at the plate most mirrors that of the Astros, but they have not been as productive as Houston and their strikeout rate is part of the reason.

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