A middle is a potentially very profitable sports arbitrage situation. It is an arb where if a match has a certain result, the arber wins one bet and gets the other refunded or winds both his bets. An Asian Handicap match illustrates the term like this:
$515 for Team1 (-3) 1.90 (Bookie1)
$435 for Team2 (+4) 2.25 (Bookie2)
The arber wins the (+4) bet at Bookie2 if Team1 wins with less than 3 goals. Total Profit: $28.75
The arber wins the (-3) bet at Bookie1 if Team1 wins with more than 4 goals. Total Profit: $28.50
The arber wins the (-3) bet at Bookie1 if Team1 wins with exactly 4 goals. Bookie2 will refund the (+4) bet for Team2. Total Profit: $463.50
The (-3) bet for Team1 will be refunded at Bookie1 if Team1 wins with exactly 3 goals. The arber will win the (+4) bet for Team2 at Bookie2. Total Profit: $543.75
Because middles can be quite profitable, it is a wise thing to bet on every middle over 0% if the arber has enough money in his bookmaker accounts. There are cases when it is also profitable to place a slightly negative arbitrage in case of a middle. The profit the arber an make is worth the negative arb percentage.
Polish middles are not very popular, but are a really good way to win money on the long term. Polish middles are a little bit similar to lays: these are not identical, but the principle way of winning is the same. To win a normal middle, you need a special outcome to happen. Well, in the polish middles, you need the outcome not to happen.
Consider a Polish Middle like following:
AH1 (-3/4) 2.25
X2 2.25
The example gives value of 2.50 and 12.50%, meaning that if this is considered as an ordinary surebet, the profit on whole stake is 12.5%, if polish middle condition is met. The 2.50 value shows the proportions of potential winnings and losses. In this case the proportion of winning is 1, and losses 1.5 (1+1.5=2.50).
If there is a bet 200 on AH1 and 200 on X2, the total investment is 400. Here the arber needs to NOT happen EHX (-1) or home team to win exactly with one goal (1:0 2:1 3:2 etc.). The average EH1 (-1) odds in ordinary bookmakers are about 3.50 (could be more). In this case the fair odds should be 3.50 * 110% or 3.85. So it means that in long term if one bets on this odd in range for example 3.85 - 4.00 one will win nothing and will loose nothing (according bookmakers).
In this case the arber plays against the bookmakers odds, or he gives a virtual odds of 2.5 for EH1 (-1) to the books. On average the virtual edge is about 54%. If one makes a series of 385 middles which are very similar to the described one, there will be an average 285 Wins and 100 Loses.
From wins one wins 285 * 50 = 14 250
From loses one loses 100 * 75 = -7 500
Total Profit: 14 250 - 7 500 = 6 750
Total Invested: 385 * 400= 154 000
TOTAL ROI%: (6 750 / 154 000) * 100 = 4.38% (this is more than one could do on average when one makes surebets)
Please keep in mind that the scenario described is only a model: there are lots of different types of middles. Playing Polish Middles can be quite risky: one can win a lot, but the chance to loose is also high, so it is good to start with small amounts of bets. But with patience, the results will come.