The AL North was the 2nd-tightest division, top to bottom (next to the NL West) last year, with only 14 games separating all 4 teams. With Toronto looking like it's made the most off-season improvement, things could tighten even more.
Chicago (85-77, 2nd in runs, 11th in ERA) needed to improve their pitching and did, signing FA relievers Sarma Nagy and Doug Bay. I think they'll miss Aaron Taylor at 2B, although new DH Don Stafford will bolster the offense. They were actually a little under their expected winning % last year...barring any big injuries they should push 90 wins.
Minnesota (81-81, 15th in runs, 1st in ERA) did it all with pitching last year, and added pitching in free agency (starters Dennis Forest and Jerry York, RP Cristobal Vizcaino). 1B Harry Rivera and RF Fred Leary both had off years; a return to normal for those 2 could add much-needed 20 HR's to last year's 178 total. I'd sure like to see them add a bat or 2 at some point, but as-is they could still gain few games on the Sox.
Detroit (71-91, 8th in runs, 13th in ERA) was pretty quiet in free agency, although they didn't have any big losses. Darwin Koch at 3B and SP Luis Perez should be at least marginal improvements over the departed Phil Hunter and Kane Delaney. The Tigers were pretty far under their expected winning % last year, so one would expect a few more wins. But I'm not convinced they've done enough to make a big run or even hold off the revamped Jays.
Toronto (69-93, 12th in runs, 15th in ERA) on the other hand, made wholesale changes. Perhaps the biggest was the trade that brought in C Pedro Caballero, although the cost was a pretty good starting pitcher (Tony Roque). I like the trade for the Jays - Caballero is 3 years younger and I love the consistent .400+ OBP. They turn to veteran Bo Benard to replace Roque, and may have piked up a key piece in LR Bailey Borders (obtained from Pittsburgh for C Miguel Julio). There were a host of smaller departures and additions...all in all, I think they've done enough to overhaul the Tigers for 3rd.
Forecast: I love the Twinkies' pitching, and I think they'll somehow scratch out enough runs to edge the Sox in a very close race. Toronto improves to finish 3rd.