Stuff about lead off hitter
Torres is maybe half a year behind Happ in terms of development and he's just as qualified to be a lead off hitter eventually as Happ is. He stole 22 bases last year and 9.8% walk rate which in theory is lower than it would actually be if he were age appropriate for leagues similar to Happ. On his career he's a .282/.355/.401 hitter. Happ on his career is .285/.380/.471. So sure, thus far Happ's shown to be a better hitter but he's also 21 to Torres' 19. On top of matters, Torres also would be a better 2B candidate defensively.
That's not a shot at Happ at all because he's obviously a quality prospect. But he's going to be 22 next year and likely in AAA. Even if you wait the full 2 years like I suggested and make him 23 where's he playing? Heyward may or may not stick around. Almora is probably in CF. Schwarber is probably in LF. Bryant's at 3B so unless you're planning on dealing Baez he's going to see more time at 2B than a rookie Happ and you're not just going to burn service time sitting him on the bench. And obviously Zobrist is likely to still be around.
On the contrary, you're not in anywhere near as much of a hurry with Torres. There's a good chance next year at 20 he could struggle in AA because let's be realistic, how many 20 year olds hit well in in AA or for that matter, how many are even in AA at 20? The average age of the southern league is 24 for batters right now. Almora hit .234/.250/.355 at age 20 in AA. Baez obviously hit much better at .294/.346/.638 but you began to see his k rate issues rise and obviously he was more of a bat first guy than Almora. Russell hit decently at .294/.332/.536 but his walk rate really suffered at 4.4% compared to the player he is. Looking it up in 2016 right now there are 3 sub 21 year olds(Ozzie Albies, Willy Adames, and Jake Bauers). Last year there were 3 also(Bauers, McKinney and Olando Arcia). 2014 there were 4(Russell, Ketel Marte, Jose Peraza and Corey Seager). 2013 there were 3(Baez, Ronald Torreyes and Yorman Rodriguez). And in 2012 there were 2(Chris Owings and Christian Bethancourt).
Since Torres is so young and playing so well you can give him the time they didn't quite see fit to with Russell. Russell is obviously a stud defensively but it's pretty obvious another year or so in AAA wouldn't have hurt him. They called him up early because Alcantara wasn't getting the job done and there really wasn't a lot of options. In the case of Torres, even if Zobrist suddenly turns to shit next year, you still have Baez. Even if you give him a full 3 more years in the minors he's only 22. 3 more years in the minors for Happ makes him 24 which is basically the cut off range of being a prospect.