MLB Betting Guide for Tuesday 9/19/23: Trusting Aces

Baseball has you covered if you want a large inventory of options to bet.

From moneylines to run totals to first-five-inning wagers, we have plenty of ways to bet the long, arduous MLB schedule daily. Outlooks can be vastly different due to starting pitchers, and a wealth of advanced stats can let us know if an individual pitcher, a bullpen, or a team is due for positive -- or negative -- regression.

Using numberFire's projections as a guide, which MLB odds from FanDuel Sportsbook are most appealing today?

Note: Lines are subject to change throughout the day after this article is published. All stats come from FanGraphs and Baseball Savant unless noted otherwise. Please check here to make sure you're seeing the most updated projections.

San Francisco Giants at Arizona Diamondbacks

Diamondbacks -1.5 (+138)

Zac Gallen may no longer be in Cy Young contention, but you wouldn't know it from his home splits.

Gallen has had some blow-ups over the latter half of the year, but he's still absolutely shoving at Chase Field. In 14 such starts, Gallen's pitched to a 2.18 ERA (compared to 4.68 away) and held opponents to a .249 wOBA (compared to .318 away). While he has given up five-plus runs in three of his last four starts overall, his overall body of work is still sublime. He's riding a solid 25.7% strikeout rate while walking just 5.3% of hitters. He still gives up a higher hard-hit rate (45.8%) than we'd like, but a matchup with the San Francisco Giants mitigates his below-average batted-ball metrics.

San Francisco struggles to generate quality contact, plain and simple. Since the All-Star break, the Giants have registered the seventh-lowest barrel rate (7.0%) and the fourth-lowest hard-hit rate (36.7%) while generating the second-highest rate of soft contact (17.0%). That's translated to some ugly counting stats -- especially against righties. In that split over the second half, San Francisco ranks 28th in wOBA (.300), 29th in ISO (.139), and 26th in wRC+ (86). They've seen Gallen twice this season, scoring 5 runs on 12 hits in 13.2 innings of work.

On the flip side, the Arizona Diamondbacks face off with veteran Alex Cobb. Cobb has been up and down in his age-35 season, pitching to a 3.62 ERA while posting a 27.8% called plus swinging strike rate. While his 57.3% groundball rate is undoubtedly elite, his 4.72 expected ERA (xERA) leaves a lot to be desired. Like Gallen, Cobb allows a ton of hard contact, clocking in with a 43.5% hard-hit rate.

The Diamondbacks lineup hasn't lit the world on fire over the second half, but they've held their own against righties, posting a .311 wOBA (19th in the MLB) and a 93 wRC+ (19th). They're also coming off a three-game sweep of the Chicago Cubs during which they put up 6.3 runs per game.

Although San Francisco holds a 6-5 advantage in the season series, Arizona has won three of four at home and covered this 1.5 runline twice. One of those came in early May with Gallen on the bump, and I'm expecting a similar result tonight.

Colorado Rockies at San Diego Padres

Padres -1.5 (-132)

We're staying in the NL West next and backing the San Diego Padres to cover 1.5 runs against the Colorado Rockies.

San Diego covered this in the opener, 11-9, and has a good chance to do so again with Cy Young favorite (-900) Blake Snell on the bump.

Snell has been nothing short of spectacular this season. Since May 25th, Snell has led all qualified starters in ERA (1.33), FIP (2.80), hard-hit rate (30.8%), and batting average allowed (1.61) while ranking second in strikeout rate (34.5%) and fourth in barrel rate (5.1%). I'm not sure what else there is to say about Snell. He's given up just two runs across his last four starts, striking out eight-plus in each outing. Yet, somehow, he may be primed for his best start yet up against what is far and away the worst lineup in baseball against left-handed pitchers.

That's right, the Rockies are B-A-D bad against lefties. How bad? Well, for the season, the Rockies have compiled a measly 68 wRC+ in that split. The difference between them and the 29th-ranked team is the same difference as the 29th-ranked team and the 18th-ranked team. On top of that, they rank 29th in wOBA (.294) while striking out at the second-highest clip (26.1%). Snell has faced Colorado twice this season. He gave up 3 and struck out 9 in just 4.1 innings on Opening Day before holding them to just 3 hits and a single run while striking out 12 later in June.

With Snell hurling, the Padres won't need to do much on offense to cover 1.5 runs.

They're well-positioned to put up a boatload of runs anyway with Ryan Feltner on the bump for Colorado. Feltner will be making his first start since May 13th after an extended stint on the injured list. Feltner has struggled to contain opposing hitters throughout his short career, coming in with a career 6.09 ERA. He didn't show much improvement in 8 prior starts this season, posting a 5.59 SIERA and walking an eye-popping 15.2% of batters.

That bodes well for San Diego's chances tonight considering how well they've hit righties.

Since the All-Star break, the Padres rank 13th in wOBA (.320), 18th in ISO (.173), and 11th in wRC+ (105) against right-handed pitchers. They've been especially hot of late, winning five in a row and six of their last seven games.

We're really only banking on the Padres to score a handful of runs in this one. With 21 runs in their last two games and given Snell's dominance, Padres -1.5 is one of my favorite plays of the season.

Seattle Mariners at Oakland Athletics

Mariners -1.5 (-120)

Sticking with our theme of backing ace pitchers on the runline, our final play today has the Seattle Mariners covering 1.5 runs against the Oakland Athletics.

Luis Castillo toes the rubber for Seattle, bringing with him a 3.69 skill-interactive ERA, a 27.2% strikeout rate, and a 33.5% hard-hit rate. While he hasn't been quite as dominant over the second half of the season, he's allowed two or fewer runs in four of his last five starts. Castillo is no stranger to Oakland's feeble lineup, having tossed 6.0 shutout innings against them back in May.

He likely won't face much resistance against them tonight, either. Oakland has been better over the second half, but they still rank just 23rd in wOBA (.306) and 18th in wRC+ (97) against righties since the All-Star break. It doesn't hurt that they've failed to eclipse 3 runs or cover +1.5 in five consecutive games.

On the other side, righty Paul Blackburn starts for the A's -- though, he may not last long. Blackburn has failed to pitch more than 3.0 innings in his last two starts, giving up 6 runs off 10 hits in just 6.0 innings of work. His ERA (4.14) is decent, but his 4.43 SIERA leaves a lot to be desired. While he has allowed low barrel (5.6%) and hard-hit (32.6%) rates, he's also given up a below-average .341 wOBA.

Seattle's offense shouldn't have any issues putting up runs against Blackburn. The Mariners have caught fire over the second half of the season, particularly against righties. In that split since the All-Star break, Seattle ranks seventh in wOBA (.338), fourth in ISO (.203), and fifth in wRC+ (120).

After taking yesterday's opener 5-0, the Mariners are well-positioned to cover -1.5 yet again tonight with their ace on the bump.

Looking for more MLB betting opportunities? Check out all of the MLB odds at FanDuel Sportsbook.

Sign up for FanDuel Sportsbook and FanDuel Daily Fantasy today!

The above author is a FanDuel employee and is not eligible to compete in public daily fantasy contests or place sports betting wagers on FanDuel. The advice provided by the author does not necessarily represent the views of FanDuel. Taking the author's advice will not guarantee a successful outcome. You should use your own judgment when participating in daily fantasy contests or placing sports wagers.