The Tigers started their 2015 campaign with a STRONG 6-0 record for the first 2 series. The top 4 players ranked in batting average in the AL are all Tigers, and the team as a whole is leading all of baseball in runs and OBP. The team's slash stats (avg./on- base%/slugging%) is .355/.433/.550, and the closest comparison to that would be Victor Martinez's line from last year - .335/.409/.565. Basically the whole team is playing like Victor Martinez did last year, only with slightly less pop and more getting on base. Since Victor finished 2nd in the AL MVP voting in 2014, its freaking amazing that a whole team could basically put up those numbers.
On top of that, the Tigers are 2nd in team ERA for all of baseball. The team has allowed 12 earned runs (16 unearned) through 6 games, scoring 47 themselves. In other words, the average score of a Tigers game is 7.8 Detroit, 2.7 Other Guys. On top of THAT, the Tigers are currently 2nd in Defensive Runs Saved (basically a stat that calculates how many runs your defense saved over or under an average defense). This is a HUGE improvement over last year, when the Tigers ranked 3rd from the bottom.
Obviously - OBVIOUSLY - not all of this is sustainable. Iglesias and Cabrera aren't going to finish the year with a .500+ batting average, the Tigers aren't going to score over 1,200 runs on the season (the 1999 Indians are the only team since 1950 to exceed 1,000 runs scored), and the Tigers aren't going to finish the season 162-0 (since beginning this post the Tigers lost to the Pirates, but I should add that they aren't going 161-1 either). So what can we draw from the Tigers' hot start and what should we be suspicious of?
Defense - Gose has looked pretty good in center, Cespedes has been brilliant in left field, and Torii Hunter was basically a stick in the mud with a glove on the end, so even JD Martinez's sub-par defense in RF is a big improvement. Castellanos is still a butcher at 3rd, but Iglesias covers a LOT of ground at SS. The defense is sustainable and might even improve as Castellanos logs more innings.
Offense - This is pretty obviously unsustainable. The offense could be really good, but they aren't going to bat .350 as a team. Iglesias and Gose will tail off eventually, JD Martinez's HR pace will eventually slow (he's currently on pace to hit 90+), and Cabrera's best season ever would be a downgrade from what he's done so far. On the flip side, expect more production from Cespedes and Victor than you've seen. I think the offense will be pretty good, but not '27 Yankees-good.
Pitching - This might be the least sustainable of the three. Verlander coming back might help (and it might not), but that bullpen is going to be a stumbling block if 1 or 2 of the younger guys (like Ian Krol or Angel Nesbitt) don't really break out. With Nathan & Rondon out already, there's been talk of the Tigers bolstering their 'pen with Rafael Soriano. This would be in keeping with their current strategy of bringing in over-priced, past-their-prime closers to fill the bullpen. The starters are passably good - Price is a legit stud, between the two of them Verlander & Sanchez should be a solid #2 & #3 (if they can stay healthy, which is a HUGE 'if'), Greene looks like a younger, cheaper Porcello, and Simon... Look, you don't need your 5th starter to pitch 250 innings, strike out 220 guys, or hold the opponent to 2 runs a game. I'm perfectly happy with a mediocre 5th starter, as long as the bullpen is good. Unfortunately, I'm not real excited about the bullpen.
Sparky Anderson always said you need to be at least 40 games into the season to properly evaluate a team (the blueprint for that being the '84 team that started 35-5). We're still 33 games away from reaching that, but what we've seen so far looks REALLY good. But the message is "let's not totally overreact". It's April, the regular season ends in October. Fortunes will be won and lost, empires will rise and fall, then rise again, hitting streaks will turn into slumps, then streaks and then slumps again... There's a lot of baseball to still be played. So, enjoy the team, but wait a minute before you get that Tigers 2015 World Champions tattoo (didn't work out too well for the Kentucky fan who did that).