2015 MLB Relative Power Index (RPI),as of the games of September 26,2015 from ESPN.GO.COM

MLB RPI Rankings
RK	TEAM	RPI	W	L	PCT	SOS	PWR	RS	RA	EXPW-L	EXPWP
1	St. Louis Cardinals	.535	98	57	.632	.503	1	627	496	95-60	.615
2	Pittsburgh Pirates	.526	95	60	.613	.497	4	677	569	91-64	.586
3	Kansas City Royals	.525	89	65	.578	.507	6	694	626	85-69	.551
4	Chicago Cubs	.523	89	65	.578	.505	3	655	599	84-70	.545
5	Toronto Blue Jays	.521	89	65	.578	.503	2	848	627	100-54	.647
6	New York Yankees	.517	85	69	.552	.505	9	735	650	86-68	.561
7	Texas Rangers	.511	84	70	.545	.499	8	707	696	78-76	.508
8	Los Angeles Dodgers	.510	87	67	.565	.492	5	635	567	86-68	.556
9	Minnesota Twins	.509	79	75	.513	.508	13	669	670	77-77	.499
10	Los Angeles Angels	.508	80	74	.519	.504	11	620	635	75-79	.488
11	New York Mets	.506	88	67	.568	.486	7	665	593	86-69	.557
12	Cleveland Indians	.506	77	76	.503	.507	15	641	617	79-74	.519
13	Houston Astros	.506	81	74	.523	.500	10	681	590	89-66	.571
14	Detroit Tigers	.503	72	82	.468	.515	22	663	773	65-89	.424
15	Baltimore Orioles	.502	76	78	.494	.505	16	672	658	79-75	.511
16	Chicago White Sox	.500	73	82	.471	.510	21	604	672	69-86	.447
17	Tampa Bay Rays	.500	75	80	.484	.505	18	606	616	76-79	.492
18	Boston Red Sox	.498	74	80	.481	.503	19	718	726	76-78	.494
19	Seattle Mariners	.497	74	81	.477	.504	17	630	696	70-85	.450
20	San Francisco Giants	.497	80	74	.519	.490	12	672	592	87-67	.563
21	Washington Nationals	.493	79	75	.513	.486	14	684	616	85-69	.552
22	Arizona Diamondbacks	.490	74	81	.477	.494	20	689	671	80-75	.513
23	San Diego Padres	.488	73	82	.471	.494	23	636	703	70-85	.450
24	Milwaukee Brewers	.486	65	90	.419	.509	28	635	717	68-87	.440
25	Oakland Athletics	.484	65	90	.419	.506	24	664	694	74-81	.478
26	Cincinnati Reds	.484	63	91	.409	.508	26	624	711	67-87	.435
27	Colorado Rockies	.476	65	90	.419	.495	27	697	815	65-90	.422
28	Miami Marlins	.475	68	87	.439	.487	25	583	644	70-85	.450
29	Atlanta Braves	.465	62	93	.400	.486	29	552	747	55-100	.353
30	Philadelphia Phillies	.459	58	97	.374	.488	30	585	782	56-99	.359

Glossary

• W: Wins
• L: Losses
• PCT: Winning percentage
• RPI: Relative Power Index+
• SOS: Strength of schedule

• PWR: ESPN Power Ranking
• RS: Runs scored
• RA: Runs allowed
• EXW-L: Expected W-L*
• EXWP: Expected winning percentage*

+The basic formula is 25% team winning percentage, 50% opponents' average winning percentage, and 25% opponents' opponents' average winning percentage.
*ExW-L and ExWP are derived from Bill James' Pythagorean theorem of baseball: Runs scored [squared] / (Runs scored [squared] + runs allowed [squared]). This formula was designed to relate a team's runs scored and runs allowed to its won-lost record.