一方、人気スポーツ弟1位の野球は他スポーツの人気の上昇を背景に、現在では多くの球団が赤字経営にあり、球団同士の合併問題も進展するなど、苦しい状況が続いています。 また、また、人気選手の相次ぐアメリカ大リーグへの移籍も国内野球が低迷する一つの要因となっています。(また appearing twice looks like a mistake to me) (with some rephrasing) Meanwhile, with the rise of other sports In popularity, baseball as the number one popular sport is now undergoing a tough time, as seen by the many teams operating in the red and talks of consolidation of the teams moving ahead. In addition, continual migration of popular players to the American big leagues is considered another reason Japan's baseball is stagnating. The rough overall structure of the first sentence is: 野球は, AA-を背景に, BB-に あり, CC-する など, DD-ています. => In the face of AA, Baseball is undergoing DD, with things like BB and CC happening. And here's the break down of the sentences. 一方, at the same time / on the other hand / meanwhile, [[人気 スポーツ 弟1位の] 野球]は [他スポーツの人気の上昇]を 背景に、 In the face of [the rise of other sports in popularity], [baseball [as the number on popular sport]] ... 現在では 多くの 球団が 赤字経営に あり, many teams now operating in the red, [球団同士の 合併] 問題も 進展する [など], [things like] talks of [team consolidations] (are) moving ahead, [苦しい 状況が] 続いて います。 [the difficult situation is continuing. また、In addition / Also, [人気選手の [相次ぐ] [アメリカ 大リーグへの] 移籍も] [国内 野球が 低迷する [一つの 要因と]] なって います。 [The [continual] migration of popular players [to the American big leagues]] is considered [another reason [Japan's baseball is stagnating]].