The Astros entered Sunday with a 3 1/2-game lead over the Oakland Athletics in the division.
That will not be the only angle, however, in the series at the Rogers Centre.
There will be the return of former Blue Jays closer Roberto Osuna, who was traded to the Astros July 30 near the end of a 75-day suspension imposed by Major League Baseball after he was charged with assault in May. The case has yet to be heard in court.
The Blue Jays obtained right-handed pitchers Ken Giles, David Paulino and Hector Perez. Giles, who fell out of favor in Houston and was demoted to the minors, has been a perfect 12-for-12 in save situations as Blue Jays' closer after going 12-for-12 for the Astros.
So, there are two closers going against their former teams.
Then, there is the brother angle.
Toronto's Lourdes Gurriel Jr. playing against his older brother Yuli Gurriel of the Astros. Each hit two home runs Friday night, the first time in major-league baseball that brothers both have had multi-homer games on the same day.
The Astros (98-57) will start left-hander Dallas Keuchel (11-11) in the opener at the Rogers Centre after defeating the Los Angeles Angels 6-2 on Sunday. The Blue Jays (71-85) will start right-hander Marco Estrada (7-13, 5.57) after losing 5-2 to the Tampa Bay Rays Sunday.
Keuchel and Estrada opposed each other June 27. Neither factored in the decision, a 7-6 Astros win. Keuchel allowed six runs and seven hits in 5 1/3 innings and is 3-0 with a 4.68 ERA in five career starts against Toronto.
Estrada gave up four runs (three earned) in five innings on June 27 and in 13 career games (seven starts) against the Astros is 2-0 with a 3.20 ERA.
The exchange of closers has worked out well for each team. While Giles has been perfect all season in save opportunities -- and not so good in non-save situations -- Osuna has been nine-for-nine in save opportunities for Houston.
Giles said he is enjoying himself more in Toronto. "I'm actually enjoying the game more than I did for my entire tenure in Houston," he told the Toronto Star. "It's kind of weird to say that because I won a World Series with that team. But it's like, I just felt trapped there. I didn't feel like myself there. Overall, I felt out of place."
"He has been perfect since he got here, and he has saved a lot of games in baseball," Blue Jays manager John Gibbons said. "I think it's a new look for him. A new team to be with. (Houston) is in the past and he is thriving."
Yuli Gurriel, who had seven RBIs and two homers Friday against the Angels, hit a two-run homer in the first inning Sunday and was 2-for-5. He is on a nine-game hitting streak, going 16-for-37 (.432).
Lourdes Gurriel Jr. was 0-for-4 with one RBI Sunday. His two home runs Friday followed a ninth-inning homer on Thursday. He became the 14th Blue Jay, and first rookie, to homer in three consecutive plate appearances.
The Astros will be trying to get right-hander Lance McCullers Jr. into a game Monday or Tuesday after his return from a right forearm strain.
"I wish we'd already clinched and had it perfectly scripted out," Astros manager A.J. Hinch said Sunday. "We have to try to win the games. If I can get him in, I'm going to try to get him in Monday or Tuesday."
McCullers worked in simulated games in Florida. "I felt good," he said. "I felt good. Over the three times I went out there, there were obviously some ups and downs, but that's just part of trying to get back into pitching shape. I was really happy with the way my body responded each time and I was extremely happy with the way I looked and felt the last time. My last outing was good, I was landing it in the zone to righties and lefties, was able to go in the zone and back foot when I wanted to."
The starter will be pitching out of the bullpen. "I've done it before so there's no reason why I can't do it again," he said. "It doesn't always work that way. There are a lot of starters you see try to make a transition to the bullpen for a limited role for the playoffs and it doesn't work out so well. I think last year because I had some success doing it, I feel confident doing it again."
Astros center fielder George Springer was given the day off Sunday because of leg and thumb injuries, but he could return to the lineup Monday.