From May 11th through the 19th, the Indians played nine games and won seven (tied with the Pirates and Rangers for best in the Majors over that span). The run has brought the Indians from third into 2.5 games ahead of Detroit for first in the Central Division. The main reason for the team's success has been very impressive starting pitching through the entire rotation.
Across those nine games every starter threw at least five innings every game, averaging 6.1 innings per start. They have not just been pitching deep into games, but they have held an ERA of 2.05 as a staff over that time (4.37 starter ERA for the season). While this run does include two amazing starts by Justin Masterson, it also includes starts by five other pitchers due to a double header. The only bad start during the 9 game stretch was by Scott Kazmir who allowed four runs in five innings. Excluding that game (the last Indians loss), brings the starting rotations ERA to 1.56.
While this stretch was impressive and the underlying reason why the Indians are on a current five game winning streak, there has been another starting trend that has went on even longer. The Indians top three starters (Ubaldo Jimenez, Zach McAllister and Masterson) have combined for 18 consecutive starts with at least five innings thrown. The Indians as a team have went 14-4 through the last 18 starts by those three pitchers including a current 12 game winning streak. Those starters have held a 3.13 ERA over that span
To break the rotation down even further, Jimenez has seemingly turned things around. He still holds an ERA on the year of over 5.00, but in his last four starts, he has an ERA of 1.90 and is 3-0. He has also maintained his strike out totals, striking out 29 batters in 23.2 innings, while eliminating his walks allowed (just 8 after walking 11 and just striking out 15 in his first four starts). This has been one of his biggest issues since joining the Tribe and his recent success proves how important Ubaldo's control is to his ultimate success as a starting pitcher. This current run of four straight great outings (at least 5.2 innings pitched and no more than 2 runs allowed in any game) is his best run since August 28th through September 21st of 2011, just after being traded to Cleveland. The Indians went 4-2 over that span and have gone 4-0 during the one in 2013, proving that Ubaldo can still be a winning pitcher, despite considerable set-backs (not limited to the entire 2012 season).
Overall, the Indians have finally discovered the winning combination of keeping the other team from scoring runs while scoring runs of their own. Since April 28th, the Indians are 18-4, going from 8-13 in last place in the AL Central to the top of the heap at 26-17 and the starters are the base of that success. The Indians have a league high five shut outs over that time and have outscored their opponents 131 to 76.
The Indians will now go on to play 16 straight days against teams that are all over .500 and competing in their respective divisions. This will be followed by two series on the road against Detroit and Texas, two of the best offensive teams in the Majors. How the pitching staff fares against these foes will go a long way to show where this team will stand at the end of the season. While the next 21 games will not immediately decide the season, a good showing in the two series against the Tigers and going at least .500 against the other difficult teams (especially Texas and Cincinnatti) will cement the Indians as a contender in 2013 and on.